Need a nice set of built-in avatars

With avatar for phone calls becoming more prominent in calls and phosh (https://gitlab.gnome.org/World/Phosh/phosh/-/merge_requests/943) it would be great to have a nice small set of readily shipped avatars images on the L5.

E.g. the N900 provided different colors of the "default avatar" (https://farm5.static.flickr.com/4082/4848327923_69a56c35cc.jpg) which was already useful to e.g. mark certain contacts visibly.

These just need to go to /usr/share/pixmaps/faces and we can just ship them in a Debian package (or even add them to calls upstream)

/cc @francois.techene would that be something design cares about?