Avatars. Is it possible to have site specific avatars using avatar plug-in

I recently installed the avatar pluggin in the hope that I could create a suite of avatars that users could select from as well as having A default avatar rather than the grey man standard gravitar for unknown responders to blogs et cetera. The documentation on the WPMU avatar plug-in page says': 'both user and site avatar options' which I took to mean that you could do as I require, i.e. Only allowing users to choose from my designs.i'm guessing its not the case but I'm unclear on this and would be grateful for any advice. If the WPMU plug-in can't do it is there anything out there that can?

Cheers

Jon