This is another one of those ridiculous ideas that I am sure will never work but if someone out there has the recourses and time here's to ya.
Remember those hologram generators like in this videohttp://www.youtube.com/watch?v=UrYWfJ7nS3w?
Here is a picture of them:
Here in Oklahoma, we built a snake room. This room had plexiglass floor with moving snakes underneath and creepiness all around. I though it would be cool to see a live snake via hologram generator. If you could make one big enough, the generator could be under the floor where guests walk. What they would see is a real snake hologram at actual size. Naturally there would be a plexiglass cover. Guests would be forced to walk towards a real snake on the floor. They would walk through a hologram.

If this were possible you can imagine the other things you can put inside to create a holographic scary image. If any of you are crazy enough to attempt this, first I will call you FRIEND, and second, here is a good place to start: http://www.greenpowerscience.com/