Interesting thread, this.
I definitely get a certain impression from
some avatars. This might include gender, too. For some weird reason cat pictures unconsciously make me assume the user is female. This thread proved my unconscious wrong already, haha.
I have to say that it's not only the visual representation which creates the outline of a user for me here, it's both the avatar and what the person writes. Sometimes it fits perfectly, sometimes there seems to be a certain divergence.
As far as my own avatar goes, I started out here a short while ago using a drawn version of my portrait. Then I got me this Munchkin expansion (it's a funny satirical card game) called "Munchkin Cthulhu". I scanned through the cards and instantly fell in love with Lloyd Lloigor - which is my current avatar. I don't think it represents any character traits.. my tongue isn't that long either!
In this particular case, it reflects what I like at the moment and I hope others might find the drawing as cute as I do.