Avatar SDK - AI-powered 3D avatars from one photo
TinyFaces - Free crowd-sourced avatar gallery including Sketch plugin
Boring Avatars - JavaScript library to generates SVG avatars based on text.
100 Free Userpics - Collection of a hundred free userpics especially for your design projects.
unavatar - Get unified user avatar
Humaaans - Mix-&-match illustrations of humans with a design library.