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.
Open Peeps - A hand-drawn illustration library.
Procreate - Procreate is the most powerful and intuitive digital illustration App available for iPad®.
Control Illustrations - 108 free flat illustrations with customizable characters
ibis Paint X - Drawn with + ibisPaint
Blush - Illustrations for everyone