I've installed a code that removes ProBoards size limits on avatars. Sometimes certain ones just look like butt when you have to shrink them to 100x100. Like...mine for instance. Seriously though, I didn't know this code was even out there, or I'd have had it since the start.
No limits now, so your favorites don't have to be squished or just funky looking out of aspect and all. I just ask that you don't go nuts, I'd still like the place to look at least somewhat uniform. Anyway, there it is. Take advantage of it.
Mine now is 200x200. To make sure yours works right, always put in the dimensions it is when you add a new avatar and it asks for it. Put the exact dimensions. I don't know that you need to do this, but I do it anyway as a fail safe.