Humaaans - Mix-&-match illustrations of humans with a design library.
Invision - Prototyping and collaboration for design teams
Avataaars - Mix and match avatars with a Sketch library
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Sketch Icons - Generate a dynamic icon library in less than 5 minutes
Craftwork - A collection of User Interface resources made by Craftwork