7
There's a way to do this in 2.0.6. Just use the User Rank Settings under System -> User Ranks.
It would replace the stars with your image, but if you're trying to display a funny "Forum Newbie" image, it might actually be helpful.
You could also create another rank where your user's avatar would disappear, and they would then have the ability to set their own avatar by editing the avatar for their profile...just set the number of posts to the same number in user ranks and avatars and it should work... Right?
I haven't actually tried this, but it seems like it would work?