Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
Smartmockups - Create stunning product mockups, easily and 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.
MockMagic - A free, easy-to-use device mockup generator
GIMP - GIMP is a multiplatform photo manipulation tool.