Not a huge history, but here is a woodcut from a 1950s edition of Kalevipoeg (the Kalevala in Estonian) that I used as my first Forum avatar. I like the telepathic image, is all.
My next avatar came after the craze for posting self-insert characters as magical girls in dreams. I came to late to that party (as usual) and my drawing posted featured my stubbornly non-magical character appearing as most of us appear in our dreams, sans pants. So my character was desperately embarrassed and trying to pull her very large sweater over her even larger pantsless hips. Understandably, this went over like a lead balloon, but I was able to adapt the embarrassed face as an avatar. It does correspond to how I feel much of the time trying to post the odd edit or drawing.