There are tons of ideas you could use...
Here's some ideas that I had. Some of which I might pursue.
Rebel/Vein: urban hood theme
Techno Viking: sky themed valhalla, norse mythos
Anna/z4 giraffe/Snare: A forest
Psychopath: Burning hospital
Agh: A factory (I know I've done armsfactory already, but it's not too great and was just a map entity test)
Iji: some sector from the game
Meower: some pokemon themed map of any kind. Could be silph co. or mount moon, or a stadium.
Sorceress: any diablo 2 themed map. Rogue's encampment, pandemonium fortress, cathedral, etc.
Shepard: the normandy ship.
Drool Warrior: Drool castle cp map (I was going to make a really cool map here)
Mojo Jojo: PPG themed map. Volcano base.
etc. etc. You can probably think of stuff for the neutral classes too.