nomacs is a free image viewer for windows, linux, and mac systems, which is licensed under the GNU Public License v3. nomacs is small, fast and able to handle the most common image formats including RAW images. NOTE: nomacs has moved: http://download.nomacs.org
Project moved to GitHub: https://github.com/reybits/simple-viewer-gl
Small and simple viewer for Linux, support multipage images, support transparency and alpha-channel in images.