You can get images on Google or whatever you choose of skeletons, add
some character to them, like the nails in this picture, and print the picture
on a thick transparency paper (the one's you would use for an over-head
projector). I made up a fake x-ray machine, plexi-glace as a screen with a
plastic frame, and I put a light bulb behind the whole thing. Worked really
well, great and cheap effect, I will post another picture of the  x-ray
and the whole x-ray machine to show it up and working. Really easy to make and it looked great in the Doctor's Office.

... and how does one make a homemade xray? (other than owning an xray machine)
Inquiring minds want to know.

ouch!!