Calibre
Calibre is a free, open source cross-platform software for reading, converting, and organizing e-book collections
OpenComic
OpenComic – free and open source cross platform program for reading comics and manga
Komikku
Komikku – online/offline manga reader for GNOME, developed with the aim of being used with the Librem 5 phone
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