Hey, you should set your avatar settings to 100x150, It's better since you are a donator, you can get the limits higher, however you have to PM a global moderator to change it, since we can't, and globals+ can only change it. I've created a guide on how to change it. http://www.sythe.org/showthread.php?t=812245
You might want to try another website, if the quality is bad.
From the rules, the limit is
Oversized avatar: Avatars have a maximum size of: 80x80 for users, 150x100 for staff and donators (width x height)
. Try not to get over that limit you can get infracted. Good Luck.