What are some alternatives?
When comparing FastStone Image Viewer and XnView MP, you can also consider the following products
IrfanView - IrfanView ... one of the most popular viewers worldwide.
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.
ACDSee Photo Studio - ACDSee becomes ACDSee Photo Studio — ACDSee Photo Studio Standard 2018 continues the ACDSee legacy
nomacs - nomacs is a free, open source image viewer, which supports mu
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
gThumb - gThumb is an image viewer and browser for the GNOME Desktop. Features Image Viewer