For decorations you could take black pipecleaners and twist them into spider bodies, and add those little squiggly black eyes.
Take cardboard and cut them into little tombstone shapes. Then paint/spray them gray. When they dry, take a black Sharpie and write "R.I.P. John Meyers" and stuff like that on them.
You could have red punch, plates of oreos, and maybe you could make some pumpkin shaped cookies or buy some of those Phillsburry ghost, bat, etc. cookies with those shapes on them.
Good luck, and if you need any more ideas, e-mail me at [email protected]