I know this may be unpopular with most people here but it would be really nice to have a theme that's more story-based than mechanic-based, for once. I know, you can always include a story but I'd love to see what people create with it as the focus. There are a TON of fun stories you can take and mold into a game (including Robin Hood, Cinderella and many others, which are public domain too, btw).

This would be a more challenging theme for me and maybe that's also what attracts me to it.

That said, I upvoted several other themes as I have many I like.