Linking invites to specific pages

I was hoping to register the User with most of the required fields in CB's registration page. One that we require is the avatar.  I see how the process works ( with \CBLib\Image\Image ) but I can't say what the final image filename will be without knowing the userid.  How does CB registration page do that, and can it be done from that registerUser function?   Or do I need to edit the user with the filename after retrieving the new userid?

That's going to be substantially more complicated then. Seams like it would be easier to just send users to CBs registration and have CBs registration accept the invite. Easiest way to do that is just use a session variable or even a cookie. The process would be Link > JEvents > Cookie/Session Variable > CB Registration > Accept Invite. That's more or less how CB Invites does it anyway.