Looks like this is turning into a FUUUUN thread (which was my real
I was talking with a friend last night and his theory is that since the SKULL "motif" really got it's start in the biker community - it was probably a self-portrait of some biker after accidentally laying his bike down on a slippery stretch of asphalt!!
It's known in their culture(?) as "Road Rash"!! My youngest brother has the permanent scars to prove that it happens!!