Darktable - darktable is an open source photography workflow application and raw developer.
GIMP - GIMP is a multiplatform photo manipulation tool.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
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.
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.
Fotor - Fotor is an all in one visual platform. It includes photo editor, collage maker, and graphic designer. You are free to make a visual look more beautiful.