Hi,
The sample avatar (the beads) is 79 x 79 pixels. A GIF or JPG format will work. You can load something slightly larger and it should resize (though it may not resize the way you want.) After you hit "update" in your profile, you should see something filled in the "Avatar URL" space. And, of course, make sure you click the "Save" button! If you are still having trouble, please post again and I'll see if one of our techie people can help.
Michelle Mach
Editor, Beading Daily
beadingdaily.com