I've had this avatar (a 3D-blocker lemming with darkish green background) since I joined here. Nothing special, actually I think my avatar is probably the blandest one here. A friend of mine made this to me when we were in high school, I just gave him the picture of that lemming and he added the background.
Years later I joined here and thought that I could use this as my avatar.
Recently I was thinking of changing my avatar for variety and fun, but didn't do that for the time being. In some (larger) forums avatars could play a bigger role in such a way that people possibly remember members from their avatars, not from their usernames, for example. I think our forum is enough small that people know each other even though avatars would change.
EDIT: Just found
this topic related closely to this one.