Re: How to change your avatar?
bbPress is linked into Gravatar. You have to get a Gravatar account, and then go into Settings in the bbPress admin. At the very bottom is a checkbox for enabling Gravatars. Click that and you should start to see avatars on the forum.
If you don’t like the “mystery man” no Gravatar picture, I’d recommend trying the bbPress Avatars plugin, which will let you integrate avatar generation scripts.