FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
digiKam - Professional Photo Management with the Power of Open Source
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
FastPictureViewer - A hardware-accelerated image viewer for the modern Windows platform.
DBGallery - DBGallery is a digital asset management cloud service (SaaS) and on-prem web-server software package for a range of team sizes.
IrfanView - IrfanView ... one of the most popular viewers worldwide.