I stumbled upon this awesome archive of fantasy images from the Manuscript Collection at Cornell. There are descriptions and pictures under the sections on the home page. You can read about the art of angels, demons, centaurs, etc. in art and what they represent(ed). One of the most interesting for me was the section on possession/insanity in fantastic art, which has less to do with demonic posession, and more to do with psychological disorders and sexuality.
Here are some of my favorite images, but if you’re into them, I would suggest checking them out for yourself here.