Throw It In: Leonardo DiCaprio accidentally cut his hand on broken glass in the scene where Candie slams his fist on the table, but continued with the scene. He can be seen picking broken glass from his increasingly bloody hand for the duration of the scene, and Kerry Washington's look of horror as he smears blood on her face was from genuine shock. The scene was used in the final cut, therefore Leo wears a bandage afterwards up until his death scene.
Tarantino had originally wanted Will Smith to play Django. The two of them discussed it a lot, but according to Tarantino the script "wasn’t 100 percent right" at the time and after agreeing to wait, he started testing other actors and decided that Jamie Foxx was perfect. Specifically, Smith has said he wanted the movie to focus more on Django, as he didn't feel the character was the true lead.
There was talk of splitting the film into two parts, like Kill Bill, but Tarantino eventually rejected the idea and cut a whole lot of the planned film. Among what was cut out includes an entire backstory for Zoe Bell's character, which explains that she wears a bandanna over her face to hide a gruesome injury. Tarantino does plan on releasing an extended cut later down the line, restoring some scenes that were left on the cutting room floor.
Though given that it is Tarantino it's best not to hold your breathe on the last part.