Image Roll
Image Roll is a free and open source, simple and fast image viewer with basic image manipulation tools
Image Optimizer
Image Optimizer is a free and open source simple program for compressing images without loss of quality using JpegOptim and OptiPNG
Koko
Koko is a free and open source image viewer designed for desktop and touch devices
gThumb
gThumb is a free and open source program for viewing and organizing images in Linux
CoreImage
CoreImage is a free and open source, lightweight and easy to use image viewer for Linux
Color Palette
Color Palette – free and open source tool for viewing the GNOME color palette
Coulr
Coulr is a free and open source small color selection program for Linux
Pixelitor
Pixelitor is a free and open source, multi-platform advanced image editor with support for layers, filters, cropping and other functions
Curtail
Curtail is a free and open source, simple and useful software for compressing images in Linux
ImEditor
ImEditor is a free and open source, simple and versatile image editing program