I don't know about you, but I feel 'over' zombies and Cthulu and things like that. Many of the most widely-used settings, characters and themes are common because they're free to use—but there's a long and endless list of under-utilized public domain works that could spark the imagination if used as prompts.
The recent Public Domain Jam has spawned a whole bunch of new works (scroll down for the games) about Captain Ahab, Captain Hook, Cinderella, Dorian Gray and lots more that any fan of classics might like to peruse.
Granbury High School Computer Club submitted Jabberwocky, a short game based on the Lewis Carroll poem (rock on, cool teens!), while Moonlight, based on the beginning of H.G. Wells' The Time Machine, looks absolutely gorgeous:
You can try Moonlight for free here.