I'd imagine a lot of people have copies of sombrero avs they themselves have used archived in image-host folders or files on HD, though some will undoubtedly have been lost already. Perhaps a "Post your Sombrero Avatar" thread might serve to round up some of the strays for posterity.
Ones I've used include:
A still version of
(found accompanying a news article about Linux users in Latin America)
I'll have to rummage on the HD of the other machine and see if I've missed any.