Humaaans - Mix-&-match illustrations of humans with a design library.
Invision - Prototyping and collaboration for design teams
Control Illustrations - 108 free flat illustrations with customizable characters
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Ouch! Illustrations by Icons8 - Professional, perfectly matching, and customizable illustrations for any designs
Craftwork - A collection of User Interface resources made by Craftwork