Had an idea here and wanted to hear what others thought.
I recently completed a project at my institution to sync user ID photos from an external database. This involved a local plugin to import the photos into the filesystem and a core hack to tell Moodle to prioritize these photos over locally-uploaded images and Gravatar integration.
I think the current avatar system could be improved. The user avatar system relies on user uploads, with a hard-coded fallback to Gravatar (if available) when there's no user upload. It's not possible to change the order of preference, nor is it possible to add other integrations without said core-hacking. Making user avatars a pluggable system (with direct upload and Gravatar as included plugins) would make new integrations such as Libravatar (MDL-29584) or home-grown solutions simple and straightforward.
This mockup shows a system with three potential sources of images:
Beyond image sourcing, I could see this improvement leading toward support for larger image sizes and other enhancements.