The statue, a natural rock formation which looks kind of like a person, bears a resemblance to the famous Moai statues on Easter Island.
The Mists of Ravenwood
In the portrait of Becky and her parents together, the mother has scrawled on the side, "Charlie and his angels ;)"
When she enters Ravenwood Park, one of the first figures the detective notices is a tree with a face carved into the trunk; it's missing an eye. The nearby sign identifies the figure as "Fangorn, Father of the Forest."
Another one for LOTR in the bonus chapter: the Ticket Seller spends most of the chapter skulking around the park trying to free her friends. She remarks to herself that "The closer to danger, the farther from harm."
The situation of a young female detective consulting a mysterious man with his own agenda locked inside a cell to help further her investigation is very reminiscent of Silence of the Lambs. The man in question even has a speech pattern which is similar to the one Anthony Hopkins employs in the film.
While you are exploring the park, you come across a recreation of a lumberjacks' camp. Your opinion of lumberjacks? "They're okay."
Possibly unintentional: Asmodai is specifically identified as an archdemon.
The Shadow of Karkhala
In the achievements screen, the symbol on the achievement for completing the bonus chapter looks exactly like the Auryn symbol from The Neverending Story.
The spelling of Britney's name is quite possibly meant as one to Britney Spears.
During the main game, the detective can find and read a letter written by someone named Xiao Mei.
