XnView MP stands for Multi Platform = it is available for Windows, Linux and MacOS. It is a continuation of the older XnView Classic. In my opinion it is a great alternative to Windows photos app or any Linux image viewer that comes preinstalled. I even think it is an alternative to IrfanView. It is really fast and simple to use, supports more than 500 image formats, has built in folder browser, image converter, editor... AND MORE!
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Priime - Edit photos with the styles of the world's top photographers. Smart suggestions, fast editing, and inspiring collections.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Nizo - A better iPhone camera for shooting film
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.
VSCO Cam - VSCO Cam is an iPhone, iPod Touch, & Android camera app w/ elegant, minimal processing options.