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.
Saint Paint Studio - Saint Paint - The Essential Image Editor
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
Stet.io - Stet.io is a high-quality pixel management platform that allows editing the pictures with online commands or multiple options with real-time effects or filters.
GIMP - GIMP is a multiplatform photo manipulation tool.
Sagelight - Sagelight is a comprehensive editing platform that allows adding multiple features to the images by improving, retouching, modifying the selective pics with high-quality work.