Unfortunately Dave, most of the artists who drew them are no longer with us, kinda hard to ask the dozen or so dead artists who overdosed what they were thinking when they drew these skulls, though one in Montreal said that is what he sees when high.  As for the rest, well Dave I am sure one can use their imagination. I would have asked the women whose bloody fingerprints on the wall I was sampling, but the deceased don't make great conversationlists.