Pick
Pick – a software for picking colors on the screen in Linux
Gcolor3
Gcolor3 – free open source software for color choosing (on-screen color detection) and color selection in Linux
Qimgv
Qimgv – free and open source fast, configurable, easy to use image viewer with optional video support for Linux and Windows
Rapid Photo Downloader
Rapid Photo Downloader is a free and open source software for downloading photos and videos for the Linux Desktop
RawTherapee
RawTherapee is a free and open source, cross-platform raw image processing program
Darktable
Darktable – free and open source cross-platform software for processing and cataloging RAW images
XnConvert
XnConvert is a fast, powerful and free cross-platform batch image converter, It allows to automate editing for your photos
PhotoQt
PhotoQt is a free and open source multiplatform, fast and simple, yet powerful and highly configurable image viewer
Nomacs
Nomacs – free and open source multiple platforms fast image viewer with additional editing functionality
Fotoxx
Fotoxx is a free open source Linux program for image editing and collection management