Gwenview is able to load and save to a variety of image formats supported by KDE applications, such as PNG, JPEG, and even the Gimp's XCF! Gwenview also sports a beautiful thumbnail toolbar when viewing images in fullscreen. Gwenview's simple interface doesn't get in the way and lets you view your images quickly and easily.
Supports simple image manipulations: rotate, mirror, flip, and resize
Supports basic file management actions such as copy, move, delete, and others
Functions both as a standalone application and an embedded viewer in the Konqueror web browser
Can be extended using KIPI plugins.