Are you writing something with multiple angles?
What genres would you love to mashup? Or what elements? (Cyborgs meet Zombies? Time Travel meets Aliens?)
I am also aware that the new TV show 'Wizards vs. Aliens' by Russell T. Davies is out too, which is a great mashup.
Personally I love superheroes or time travel with anything. Dystopian would work well mixed with historical, or time travel or something different. Steampunk meets romance?