Suggestions for sub-theme for Halloween contest?

We will host a halloween contest here at the Pokeshippers, but not just an ordinary halloween themed contest - something more restricted like a sub-theme, as MirakuruNaito suggested.

Here is her original idea:

"maybe there should be a few restrictions or themes present? Like setting the contest to a song commonly associated with Halloween or making the theme into something like the common things that are done on Halloween rather than simple just dressing up (trick or treating, bobbing for apples, Dia de los Muertos, whatever)."

This to prevent just "normal" halloween pics where the characters are just dressing up, and instead get a twist t the whole thing if you know what I mean.

So, comment with suggestions on what sub-theme you would like