Custom User Avatars

Hi,

I am setting up a WordPress-based website for users/members and want to provide a set of kid-friendly custom avatars for them to select (i.e.: not upload their own). I have been looking at a few plug-ins so far, but most of them offer Gravatar integration which is not what I want.

Any idea of a simple way I can provide a set of say 20-40 already-designed pictures that members can select from during and after their sign up process?

Cheers!