Hi, I am the developer of the Openvatar service.
I can't speak German, sorry.
I want to explain the system a little more.
Gravatar service joins the user mai to an avatar, openvatar joins the user openid to an avatar, it's simple.
Like Gravatar, Openvatar also needs an image.
Every time someone uses his openid to identify, his picture appears bellow his openid, it's all. For exmaple, my avatar on this comment.

Greetings.