Being GitHub anyone may submit new avatars (those with wings attached directly or indirectly to the arms) but if you are not familiar with git, GitHub, or making pull requests I can assist with getting unrecognized avatars into the system.
Easiest way is to share a public version with me and I’ll handle the rest for you, but providing a screenshot from the debug panel (showing the hashes), a photo of the avatar, and creator information also works.