I increased the max pixel size to 100×100 for avatars but bigger than that the html will take over and try to resize it. So your best bet is to create your original graphic so that it is under the limit and html is not forced to take over.
Create your graphic to be 100×100 and it will not be resized by html.
Unfortunately html tries to make every graphic 100×100 and I have no control over that, except allow no limits which means people can upload absurdly large avatars.