I was thinking, when you rank up, you get a new avatar on your profile, but lose the old one. Wouldn't it be awesome if there was an avatar page where they were all blacked out, but as you ranked up you unlocked the images and could look back at the old ones? Perhaps still keeping your most recent rank's avatar on your profile page though? As it is, once you move up a rank, there's no way to view old avatars anymore, that I can tell...
