Never changed my avatar, never will. When you see the smart ass rabbit with the helmet, you just know it's *me.*
As for signatures, I'm old school on this regard. A signature is words, preferably your own...
'Pretty swallow cuts,
The dawn falls open in twain...
Sun may rise today.'
--Some long-eared freak with a sword
Zoom's spaceshuttle landing video
(This is what happens when you let a rebel fighter pilot land expensive government hardware...)