Verified answer

you definitely have to get a sound system going with songs everyone's gonna like.

if you're going to make it a halloween party, i think it would be fun to have someone dress up as a scarecrow & wait for the guests out front, & freak them out as they arrive :)

as far as decorations go, im sure you can find tons of cheap, seasonal stuff at any store...tons of spiderwebs. strobe lights would make a creepy effect (first make sure no one will be affected by the lights, ex: someone autistic)

For Halloween ideas you could cut like bats and ghosts out of paper and string them on the twine.

Since you have a barn, you might have animals, have an animal party. Or maybe a PJ party. Have it at night when the stars are out and you can all lay on your backs and watch the stars.

You could do a Murder Mystery Game/Dinner. They sell the kits, you provide the pizza and a CD player. Lots of fun!

http://www.dinnerandamurder.com/

your theme can be coming out of the closet...