Trigraphy - Photo editing app that allows you to make mosaic/abstract looking art.
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Dreamscope - Make and share 'deep dream' images using dozens of supplied styles or your own.
Pixel Studio - The Pixel Art Is Always Fun
Photomosh - Turn anything into a vaporwave
Pixel Art to CSS - Draw and animate pixel art, export the results to CSS