Open Peeps - A hand-drawn illustration library.
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Control Illustrations - 108 free flat illustrations with customizable characters
Clip Studio Paint - The artist's software for drawing and painting.
DrawKit - MIT licensed SVG illustrations, in 2 styles
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.