SomethingAwful has had something like that since the early 2000s as well, with some things being purely status, like paying an extra $10 to get a bigger avatar image. Also introduced as a (successful) solution to their previous lack of success monetizing via ads.
(I believe, at least for a while, you could also change someone else's avatar for something like $20 or $30, and they could pay some similar amount to insure it against changes.)