ImageGlass - You can use Image to view your digital images and photos of many different formats.
digiKam - Professional Photo Management with the Power of Open Source
IrfanView - IrfanView ... one of the most popular viewers worldwide.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
FreeVimager - Free & Fast Image Viewer and Editor for Windows.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.