300: Rise of an Empire provides examples of the following tropes:
Absentee Actor: Even though Leonidas appears in archive footage and is mentioned as being an important figure in the story, no new footage is shown of the character. In spite of this, most of the characters from the first movie end up reappearing in flashbacks of their own.
In the original film/comic, Xerxes is just an inexplicably tall dude. In Rise of an Empire it's explicitly indicated that he really is a supernatural being (essentially he's pretty much a Goa'uld), or at least he has reasons to think himself as one.
The Persian Emissary personally trained Artemisia in combat.
Adapted Out: In real life, one of the key figures in the battle of Salamis was Sicinnus, Themistocles' The Lancer, Battle Butler, and The Spymaster, who served a crucial role in Themistocles' strategy. He is completely absent from the movie, and his role is made moot due the different circumstances of the battle in the movie compared to real life.
All Just a Dream: After Themistocles falls deep under water after his ship was destroyed, he sees large, monstrous sea creatures killing and devouring several Athenians (with one then lunging towards him). Thankfully, it was only a dream.
Aluminum Christmas Trees: You may have a hard believing that the Persian Empire had a female as commander of its navy, but Artemisia was a real person.
Xerxes really built a bridge out of ships to cross into Greece. The movie didn't show him ordering the ocean to be whipped after the first attempt collapsed.
Anachronism Stew: Among other things almost every Persian foot soldier in the film seems to be armed with a Khopesh. A Canaanite and Egyptian design that had been retired from service for about 1000 years by that point.
Arc Words: "Avenge him" not only for Queen Gorgo, but for both Xerxes and Artemesia as well.
Armor Is Useless: The relatively fully-armored Persian troops' gear is largely ineffective. Justified, because they all wear light armor due to the style of warfare in Asia being different than the Greek style. On the other hand, while the Greeks go into battle with only helmets and bracers, both of these are actually used many times to deflect blows and arrows.
Artistic License - History: Like the original comic and film, it's loosely based on true events as reported by the ancient Greek historian Herodotus.
It includes such inspiring conceits as Themistocles killing King Darius at the Battle of Marathon (he wasn't present at the battle and died well after it and in different circumstances) and Xerxes being driven by the desire to avenge his father.
Darius didn't invade Athens because he was "annoyed by Greek freedom"; he did it because he was fed up of having to deal with Greek-backed revolts in his territories. On that note, Persia was the place where slavery was outlawed while it was perfectly legal in Greece and actively enforced in Sparta, and democracy was only available to certain noble-born men.
Artemisia dying at the hand of Themistocles during the Battle of Salamis, even though she actually survived in Real Life. By attacking other Persian ships to trick the Greeks no less, something that given her personality would be perfectly in-character.
Xerxes burning Athens to the ground, even though historians greatly theorize that Xerxes burning Athens was Greek propaganda, and Xerxes had no reason to destroy a city of significant strategic value. (Something noted by Artemisia. On the other hand, Herodotus himself claimed that burning the city was the entire objective of the campaign, which is why Xerxes withdrew with most of his forces shortly afterwards.)
Like the previous movie: Hoplites aren't equipped with armor.
The scene with Artemisia insisting that she be allowed to pursue the Greeks to Salamis, with Xerxes trying to dissuade her and noticing that it's tactical suicide, portrays both characters exactly backwards from how it was recorded in the histories (where it was Xerxes who wanted the big push to crush the Greeks).
The Immortals get modified masks and heavier armors in this film in contrast to the first one. Also, the film shows a maskless kind of Immortals which look like regular Persian humans and not disfigurated ninjas.
The Persians themselves actually look like they might be from Persia this time around, as opposed to the Africans and Indians of the first film.
Ascended Extra: The Persian messenger from the first movie was no more than a named extra, but in this one he's revealed to have been a Parental Substitute and The Obi-Wan of sorts to our resident Dragon-in-Chief, Artemisia. He still appears very little in the movie, but this time around he has a lot more impact in the narrative.
The Atoner: Ephialtes' guilt over his betrayal is making him slowly slip into this. He says outright that Themistocles would be justified in killing him.
An Axe to Grind: Xerxes uses a big fancy one to behead the corpse of Leonidas. He ordered this done in real life, and the corpse was also crucified.
Authority Equals Asskicking: If someone is leading people, expect that someone to be a total badass in combat. Themistocles is the leader of the Athenian soldiers and their best warrior. Artemisia is the finest warrior in all of Persia. Even one of Artemisia's commanders is shown felling multiple Greeks by himself when his back's to the wall.
Bigger Bad: In Artemisia's case, she's this for the first film - she convinced Xerxes to reshape himself into a God and declare war on the Greeks after Darius told his son to stop fighting against them.
Big Good: Leonidas is a posthumous example, as his Heroic Sacrifice is what convinced the Greeks to go to all-out war against the Persians.
Bolivian Army Ending: So... did the Greeks won after all? Or did Xerxes and his giant army defeat those last remaining warriors and complete their victory? The movie is not clear, we saw the warriors charging into battle, and then closing credits. If we're looking to history, then the Greeks did win the battle of Salamis.
Chainmail Bikini: In a rare inversion of the trope it is the male combatants who partake in this. The females wear gowns that, while not providing much more in the protection department, show a lot less skin.
Color-Coded for Your Convenience: Athenians wear blue capes, Spartans wear red ones, and the Persians have dark armor (as a matter of fact, every single person in Persia seems to wear nothing but black with at most details of gold).
Color Motif: The first movie had a very red/orange atmosphere, and the Spartans wore red capes, while in this one everything looks varying shades of blue/black, and the Athenians wear blue capes.
Composite Character: Artemisia as portrayed in the movie is a fusion between the historical Artemisia and the historical (male) Mardonius. It was Mardonius who acted as Darius' proud chief enforcer (and not Artemisia), Mardonius was the childhood friend and advisor of Xerxes (and not Artemisia), it was Mardonius who convinced Xerxes to invade Greece (though using less machievellian methods than Artemisia does in the movie), and Mardonius died while Artemisia did not in real life, while in the movie Artemisia dies..
Dark Action Girl: Artemisia was trained by Persia's finest warriors until she surpassed them. Themistocles believes if he is dead, not a single man amongst the Greeks will be able to match her skill. It's proven when she cuts down multiple Greeks without breaking a sweat.
Elite Mooks: The Persian Immortals that serve as Artemisia's guards. Unlike when they fought the Spartans, they're able to cut their way through dozens of Greeks at Artemisia's side.
Femme Fatale: Artemesia planned to seduce Themistocles into joining her side. While the method proves effective, things still didn't go as planned.
Fly-at-the-Camera Ending: The film closes as Themistocles lunges toward a Persian, who happens to be in the POV of the camera.
Foregone Conclusion: Anyone with knowledge of the greco-persian wars will know that the Greeks will win the Battle of Salamis and that Themistocles, Artemisia, Xerses and Gorgo will survive the events of the film. Ultimately subverted in Artemisia's case who dies on Themistocles's sword.
For the Evulz: According to the film, Darius wanted to invade Greece because he hated the Greek freedom. Apparently, the Greek support to the Ionian revolt against Persian rule had nothing to do with it, though it's possible the Greeks didn't see that as them doing anything wrong.
The Greek rowers don't seem to be particularly well treated, though they don't complain. They might be free men however, as ancient Greeks didn't use slaves to row in their triremes, contrary to popular belief.
In contrast, the Persian rowers are slaves, chained to their posts and whipped to continue. The Greek rowers are free men, as the one time we see them they are unchained.
General Failure: As far as Artemisia is concerned, all of her generals are this. She herself may count as one.
Genius Bruiser: Themistocles is a brilliant strategist and a formidable fighter.
Gone Horribly Right: Artemisia wanted a God-King out of Xerxes for her to influence. And she got one.
Historical Badass Upgrade: Themistocles fought in the Battle of Marathon, but he did not devise the strategy or lead the charge (he was but one of many captains involved in the struggle) and did not kill King Darios (who, as mentioned above in Artistic License - History, died in entirely different circumstances). He didn't kill Artemisia either.
Historical Villain Upgrade: The Persian empire is on the receiving end of this again. Also It's doubtful that Queen Artemisia was this psychotic in real life where she just happened to be the Queen of one of Xerxes satraps who took his side in the Greco-Persian wars. Another mention must be made of King Darius I, who invades because of his hatred of Athenian freedoms. Not because he was getting a mite sick of Athenian-sponsored revolts in his home town as per reality.
Hollywood Tactics: Riding a horse in a naval battle. Though he may have been counting on the absurdity to help it work. The Athenians running into Marathon with double headed battle Axes and generally fighting more like Celts than Greeks is notable because Athens won the Battle of Marathon for reasons similar to the Spartans success at holding the hot gates for as long as they did. The heavy phalanx based hoplites overpowered the light Persian infantry and provided no room for the Persian cavalry to maneuver on the crowded beach caught between the Athenian line and their own boats, though they did break formation and charge in order for their slow-moving phalanxes to not be picked apart by Persian archers. Had the actual battle been fought like the one in the movie the Athenian forces would have likely been swarmed and obliterated. It's somewhat justified that the narration says that Themistocles has the Greeks charge while the Persians are still unloading their troops, leaving them without their horses and without a lot of their troops being able to get off.
Honey Trap: The normally heavily clad Artemesia dresses in a Stripperific attire when she tries to talk Themistocles into joining her.
Hypocrite: Artemisia is one. After the Persians destroy Athens she acts like she knows more than Xerxes because she "helped" him become king. Xerxes ends up doing a lot more than she does and is proven correct in the end when her impulsiveness leads her to defeat at Salamis.
Interquel: Technically one, since the Battle of Salamis took place before the battle of Plataea, which 300 ends with. The film also features Xerxes's backstory, including the Battle of Marathon and his ascension to the throne.
Interplay of Sex and Violence: Artemisia and Themistocles feature a scene in the former's ship which it's hard to tell whether it is a fight, a nookie or both.
Artemisia: Die with me every night and rise with me every morning.
I Owe You My Life: Part of Artemisia's loyalty to Persia (or at least to King Darius).
Jerkass Has a Point: Artemisia may be annoyed at his insolence, but Xerxes is actually right in everything he tells her before the movie's final battle.
Karma Houdini: In one of the few bits of historical accuracy of the movie, King Xerxes survives the events of the movie unscathed (unlike the previous movie where he was wounded by Leonidas).
Lady of War: Artemisia and Gorgo, both of whom actually fight at Salamis and get a sizable body count.
Large Ham/ Evil Is Hammy: Xerxes at full force! Extra points for the over the top throne that helps in emphasizing him in this way.
Non malevolent and lesser example goes to Themistocles who is full of Rousing Speeches.
Last Villain Stand: Artemisia is outnumbered and outgunned, and is aware that she's going to die. Themistocles gives her one last chance of redemption, but she metaphorically spits at his face and charges one last time to battle, before being struck down by Themistocles once and for all.
Maybe Magic, Maybe Mundane: The films shows a trippy sequence in which Xerxes becomes a god by passing a ritual on a strange cave in the desert. While it is outrigthly stated by the Unreliable Narrator to be an hallucination, we never are told whether it really was or not.
Meaningful Name: Why is "300" on the movies title even though its not focusing on the 300 Spartans? Because it's on the number of Greek ships, which were over 300.
Mook Chivalry: Subverted. Artemisia's guards team up on a number of Greeks, though Themistocles is able to kill them all regardless.
Mook Promotion: Artemisia needs a second in command. She keeps selecting random mooks for that, and kills them when they fail.
My Greatest Failure: Themistocles launched an arrow that mortally wounded King Darius at the Battle of Marathon. He now knows he should have felled Xerxes instead, and many, many men have died due to his failure then.
Off with His Head!: Xerxes beheads the corpse of Leonidas. Artemisia also beheads a captured Greek near the beginning of the film.
The Oner: Themistocles riding through the battle on his horse at the end of the movie is done from the time that he jumps onto it to when the horse's legs are cut out from under it, leaving Themistocles to hit the deck.
Revenge: One of the main themes of the movie. Artemisia wants Greece to burn in revenge for her family's brutal murder and then being sold off as a child sex slave for several years until she was left for dead. Xerxes wants revenge on the Athenians for the death of his father Darius and the Persian defeat at Marathon. Gorgo and the majority of the Greek City States want to avenge the 300 Spartans for their sacrifice.
Revenge Before Reason: Artemisia becomes so obsessed with killing Themistocles that she walks right into a trap.
Rock Me, Amadeus!: The movie ends with a remixed version of "War Pigs" by Black Sabbath. Generals gathered in their masses, Just like witches at black masses. Evil minds that plot destruction, Sorcerers of death's construction. In the fields the bodies burning, As the war machine keeps turning. Death and hatred to mankind, Poisoning their brainwashed minds. Oh lord yeah!
Themistocles will also give a few of them. Two shown in the trailers:
Themistocles: Let it be shown, that we chose to die on our feet, rather than live on our knees!
Themistocles: Steady your hearts! Look deep into your souls! SEIZE YOUR GLORY!
Sadistic Choice: He may have not realized it, but Themistocles' offer to Artemisia (escape or die) was this. What would happen to her if she escaped? Xerxes would kill her, and of course she may not hope to be welcomed among the Greeks. So, her actual choices were "die in some hours or days, or die right here and now", and she preferred the later.
Shadow Archetype: Themistocles and his Athenian squad shows many parallelism to Leonidas and the brave 300. For instance, Scyllias and Calisto are respectively Foils to Artemis and Astinos.
Smug Snake: Artemisia is not nearly as clever as she thinks she is. Despite her manipulating Xerxes into becoming king and declaring war on Greece he actually is proven right at the end. If Artemisia had taken his advice and sent a probing force to make sure that Salamis wasn't a trap, the Persian navy wouldn't have been destroyed.
What the Hell Is That Accent?: Australian Sullivan Stapleton portrays Themistocles with an accent that's all over the place, standing in some sort of bizarre limbo between Scottish, Irish, Australian and Queen's English.
Who Is This Guy Again?: Scyllias' name is actually never stated in the entire movie. Calisto's, his son, is only said once in the scene where they have the secret conversation with Themistocles.
Artemisia watched as her family was violently killed along with the rest of her city, and is then captured by Greek soldiers that rape and beat her until they leave her on the side of the streets to die.
Xerxes, surprisingly, also gets thrown into this territory when we see how broken he was by the death of his father as a young man.
Would Hit a Girl: Artemesia always gets the receiving end of this. First the Greeks who killed and raped her family gave her a bog boot before being sold to slavery. Then in the Final Battle, Themistocles gives her a solid hook, again, to the face.
(to Themistocles) Artemesia: "You fight harder than you fuck!"
Would Hurt a Child: As written above, Artemesia went through shit because of the bastards who killed and raped her family, to the point that she was left to die on the streets.
You Cannot Kill an Idea: The Persians may conquer all of Greece and burn Athens to the ground, but the ideas of freedom and democracy will live on.
You Have Failed Me: Artemisia has the first general to fail at defeating Themistocles clapped in big, heavy manacles and thrown into the sea. At least he knew this would happen before hand.
Your Size May Vary: Xerxes' height varies quite a bit in the series. In the original 300 he was unusually tall, but his height was still reasonable for, say, a Harlem Globetrotter. In Rise of an Empire, he's a good 10-12 feet tall, which is much taller than humanly possible and seems to be due to the film establishing that he really is a god-like being.