bbPress.org

Try the User Photo plugin. It is available for bbPress and WordPress:

https://bbpress.org/plugins/topic/user-photo-for-bbpress/

https://wordpress.org/extend/plugins/user-photo/

It worked easily for me. Just need to make the right settings – set the same paths to image folders and keep the original function calls to avatars if you want to use Gravatars when available.