
meh - meh is a small, simple, super fast image viewer using raw XLib. KuickShow - Fast and convenient image viewer for KDE. Koko - Image viewer designed for desktop and touch devices. imv - Lightweight image viewer with support for Wayland and animated GIFs which uses FreeImage. ida - X11 application (Motif based) for viewing images. Gwenview - Fast and easy to use image viewer for the KDE desktop. GPicView - Simple and fast image viewer for X, which is part of the LXDE desktop. Geeqie - Image browser and viewer (fork of GQview) that adds additional functionality such as support for RAW files. feh - Fast, lightweight image viewer that uses imlib2. EyeSight - Image viewer for the Hawaii desktop environment. Eye of MATE - Simple graphics viewer for the MATE desktop. Eye of GNOME - Image viewing and cataloging program, which is a part of the GNOME desktop environment. Ephoto - A light image viewer based on EFL. Deepin Image Viewer - Image viewer for Deepin desktop. CoreImage - Simple lightweight easy to use image viewer based on Qt. Features include Vim-like controls, rotation and zoom, zoom-to-fit, and fast multi-threaded rendering. MPLAYER VS VLC PLAYER FOR FLAC PDF
jfbview - Framebuffer PDF and image viewer based on Imlib2.fim - Highly customizable and scriptable framebuffer image viewer based on fbi.
fbv - Very simple graphic file viewer for the framebuffer console. fbi - Image viewer for the linux framebuffer console.
See also Wikipedia:Comparison of image viewers.
1.5 Game and interactive application development.