Hey David,
Have you been to this site yet?
Espectro
It's got a ton of art pics (classical and new). A lot of it would need cropping to make an avatar, but they might work anyways.
Here's one that I would like to see turned into an Avatar (for myself of course):
Pablo Perez; Cat (2003)
And if anyone likes fish, this one might work too (just crop the part with the fish in the bottom left corner):
Flou y la arcoiris (2002)
I'll see if I can find more pics for you to ply your trade on
