Hunh. Interesting. My reaction is certainly not that s/he's neopagan. Aside from the wolf-motif, I see nothing there to give that impression, just an artist who saw an opportunity to use an unusual medium. I'm as curious about what gave you the impression he* was neopagan as the assumption of your flatmates that he was a psycho.

I don't think he's especially likely to commit murder, but it IS somewhat weird for someone to smash their thumb and think "hey cool! I can paint with this!" I can understand why your flatmates were weirded out.

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*And while the artist could be male or female, I certainly get a masculine impression. *shrug*