Well. Theme isn't needed (could be used, though), but genre (romantic, gothic, etc...) probably is, just to enable comparison.

For organisation I'd suggest a simple thread with a 'post 'em here' along with a secondary discussion/comments thread, and then open a 'Vote for 'em here' thread once the submission deadline's been reached.

Maybe we could have a *best romantic* and *best non-romantic* award.

As themes,
Lovecraftian horror, cats, night, day, sun, battle. Anything really would do. I think it's easier to work without them (maybe just me, since my work is mostly just developed improvisation).