Update: I have figured out a way to practical way to produce the Pepper's Ghost Effect in an outdoor situation, so I have updated this instructable with the results, jump to the last step for if you want to see the result.
I wanted to add a personal stamp to our Pirate Ship decor for Halloween, and also to get my girls involved
in the whole process. This effect is very easy, and could be used to project skulls or other face paintings on your walls to give your guests a spooky welcome. If you want to get a little more fancy you could also combine the floating skull with a "Pepper's ghost holographic effect"
to scare the pants off any unsuspecting trick-or treaters.