it's not an "option," it's a bug
this
i'm not against the large avatars and think that if the forum were better formatted for them they'd look really nice; but fact is badspot didn't intend for them to be uploaded this way, and he's not going to put his time into making it a possibility when you guys basically just laughed in his face about how you worked around it. the thing that is likely the easiest for him is to remove the avatar rights of the people who changed it. if he's on his good side, he might restrict all uploaded .ico files to under 75x75 or remove .ico from being used entirely.
everyone participating in using the big avatars can have their fun now, but it's pretty much guaranteed they won't still have them, one way or another, by the next time badspot is online.