what demographic does my art sell too?

Well I'm no expert in this sort of thing but your art has a rebellious tone, in fact a cult tone as with the picture of the Manson Family. That is who they are right? So I believe the audience is narrow. However I'm sure there are people who are into this kind of art and perhaps someone here can help you with suggestions of marketing them.

I can't tell what media you are using. Are they drawings, paintings, or digital?

As for myself, I'm just a hobbyist and don't expect to make any money so I haven't researched that avenue.

OK obviously I'm from a different generation. LOL Sorry about the mistake. I believe your audience is young people and people that are into Metal music. I don't qualify but my son I'm sure would love it. He's no teenage, he's 43 but is really into the metal music. Wish I could help with advice on marketing. Surely this site will wake up one of these days and get active again.