60x60, is kind of tiny. Whenever I find an avatar I like, it ends up looking horrible when it's shrunk down to size. I feel like 100x100 is a more reasonable, standard avatar size. Also, it matches the size of our stamps!
As for the size limit of 10 kb, that seems quite small to me. Is there a reason it has to be so small? Some people like to have animated gifs as their avatars.