Place Cards and Holders
This is my all time favorite idea for a place card holder. You hang whatever place card design you like from a creepy tree...too awesome.
Chandelier Place Card
Black and White Checkered Place Card
Victorian Frame Place Card Holder
You could also use edible ink and use red or green apples for place cards and healthy favors!
How about using some of Martha's lantern ideas for table numbers?
You could also name your tables after creepy characters like "Ichabod Crane" or "Michael Myers." You could also try using scary movies, or couples in scary movies or stories (Frankenstein and Bride or Christine and the Phantom).
How about mini pumpkins with table numbers painted on or regular size pumpkins for table numbers?