I agree that it is more than one image layered. It makes sense considering the inconsistencies of the details.
Feynman is right about the speed at which certain details are viewable.
I think with the pubic hair and the penis, it was an actual photograph, photoshopped to look like an x-ray image. Doctored image or negative and then combined that with an actual x-ray image of a skull. Maybe the same with the hand since no actual bone structure is visible.
Barium powder could've been used. Metallic powders...
Here is what the photo looks like with the grey scale inverted. Looks more like an actual x-ray. The image(s) are still not correct as far as detail is concerned.