3dicons - 3dicons library offers beautifully designed open-source 3D icons.
Ouch! Illustrations by Icons8 - Professional, perfectly matching, and customizable illustrations for any designs
ICONZ - ICONZ is a premium icon library that offers more than 70 unique icons for all your products.
Control Illustrations - 108 free flat illustrations with customizable characters
Wannathis - 3d illustrations and freebies
Humaaans - Mix-&-match illustrations of humans with a design library.