Use local file for avatars before falling back to initials

I love the new avatar usage in the graph.  But not all of my team members use gravatar, and we can't force them to.

Can we have a local list (XML, json, csv, anything) where I can map an email address to a local folder that contains an image for my team members? It'll be visible for me, and only executed when the email doesn't have a gravatar image.  

(1) Grab from gravatar | `avatar.serverUrl`

(2) Grab from local map

(3) Fallback to initials