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.
Artboard Studio - Online graphic design app mainly focused on product mockups.
Artrage - A simple but lovely natural media painting and sketching program.
Canva - Canva is a graphic-design platform with a drag-and-drop interface to create print or visual content while providing templates, images, and fonts. Canva makes graphic design more straightforward and accessible regardless of skill level.
Procreate - Procreate is the most powerful and intuitive digital illustration App available for iPad®.
Image to Sketch - Convert images to pencil sketches with AI technology