That is something that has been looked into and we have discussed a few different options- I will bring it up again at the next town hall meeting tho as we do need to act on it. Members should be linking to an image that is the same size as the image posts at, not to a full size file.
In the meantime please PM me with the member names of those you've found and we will act upon them. We do remove avatars that are linked to large files, particularly the animated ones, as we run across them but there are simply to many members for us to find each one daily.