It is well worth downloading Gimp 1.3 (aka Gimp 2.0 beta) if you find the original Gimp interface a bit daunting. Now has all those 'right click' menus available as a menu bar in your image window. But if you are like me, it is just as simple to continue right clicking
A small scale painting program for GNOME, based on XPaint.
A "reasonably versatile" bitmap editor, supporting jpeg and png formats.
Panorama Tools, Hugin and Enblend
Photo stitching tools. Panorama Tools are command line programs to stitch two or more images together in a variety of mindboggling ways. They are available in RPM and .deb formats from the website. Hugin is a GUI front end to Panorama Tools. There are Windows and RPM binary downloads available, but compiling is straight forward, assuming the documented development packages are installed. Also, you may need to check a g++ symlink is in place before compiling. Hugin has a lot of options and features, so reading the simple tutorials on the website is recommended. However, the options all have sensible defaults.
Enblend is another command line tool. It helps to, err, blend colours between multiple images created with Hugin. Enblend is available in Windows binary and source code for Linux, but compilation is easy following the documentation. There are sample results on the website.
Documentation for installing this software on Debian is on the LinuxHints/PhotoStitchers page.