Originally posted by fury
The avatar dimension size is much bigger here than it is at many other places. If we were to make them much bigger, there's the chance someone will upload an extremely huge avatar, and every time they post to a thread, it will stretch out the left column of the post tables, thereby squeezing in the right column, which contains the actual post. In cases where the user is browsing with a very low resolution or browser window size, the space is already pretty tight.
I do think the file size could stand to be upped slightly, if only to make it a bit easier on a lot of people who seem to be just barely over the 24000 byte limit. There are only 528kb in avatars but there are over 11 megs in attachments, which are limited to 100kb in size.