If you want to make a memorable Halloween Display have a look at these Singing Halloween Pumpkins by davidandora. A video projector is used to shine images onto the fronts of the pumpkins in such a way that it looks like they have been carved. The effect is very real looking.
“The illusion of the singing pumpkins is created by projecting animated features onto uncarved pumpkins. It is particularly effective because the only content in your projected animation are the carved features of each pumpkin. The rest of the video image is black, or no light when translated to a projection. The brightness of the projected animation reflects off of the pumpkin and appears to emanate from within, even casting a glow in front of the pumpkin as it would if it were actually carved and internally illuminated.”