I like the pic Terra posted. I think the Zombie Prom is a great idea! We used to get a big group of art majors to dress up as zombies and meander around campus for a few hours on halloween night. The first year there were only 10 or so the next about 50. Maybe you could incorporate a costume contest for the liveliest zombie. Fake blood is pretty cheap and you could splatter it around everywhere to make a massacre scene.