Snape's potion cabinet: OK, so this is both Harry Potter-centric and Halloweeny, but it's sufficiently spooky to do both, and you can keep it on display all the time to show what a superfan you really are.
The Pointer: The key to any great decoration is versatility, and this guy absolutely has it. Use him to point guests to the bathroom, point kids to the candy, or point innocent bystands to their doom ... your choice.
Jersey Devil sign: This is the perfect thing to advertise the museum of wonders you have in your house this Halloween. Of course, you better be prepared to deliver the goods, or you might get plenty of tricks sent your way.