Darktable - darktable is an open source photography workflow application and raw developer.
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.
Adobe Lightroom - Adobe Lightroom is a family of image organization and image manipulation software.
Autodesk SketchBook - SketchBook drawing and painting software provides designers, architects, and concept artists the tools to sketch ideas quickly and create beautiful illustrations.
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
Clip Studio Paint - The artist's software for drawing and painting.