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.
Artrage - A simple but lovely natural media painting and sketching program.
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
PaintTool SAI - Learn to draw in different ways.
Clip Studio Paint - The artist's software for drawing and painting.
SketchBook - SketchBook is a professional drawing or painting application that allows designers, architects, and concept artist to sketch their ideas and create adorable illustrations in no time.