Your part: throw down any cool ideas for a scene that is Halloween related (provide links to references for the more obscure stuff please). I'll pick and choose from the ones I like (or is asked for the most) and draw as many as I can.
Keep the suggestions on subject/theme. Don't throw in random characters just because you like them or tossing down a scene with a harem full of characters will definitely be lowered on the list. Some funny twists, simple but on theme, or inspired crossover would be higher on the list.
Brainstorming is probably the most rewarding part of the creative process so have fun everyone!