XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
GIMP - GIMP is a multiplatform photo manipulation tool.
BatchPhoto - BatchPhoto is a batch photo editing software for Win and Mac that can convert, resize, annotate and watermark hundreds of photos in one go. Learn more and try it for Free!
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.
Batch Image Converter - Convert multiple images, photos, and pictures between 30+ formats: JPG, PNG, GIF, TIFF, BMP, JP2, J2K, TGA, PSD, RAW, DDS, PNM, WMF, ICO, SGI, HDR, LBM
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.