XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Smart Pix Manager - Smart Pix Manager is a powerful and reliable solution for the management and viewing of all documents, common images, sound (WMA, MP3), and video files (AVI, MPEG), etc.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
StudioLine Photo Basic 4 - StudioLine Photo Basic 4 is a sophisticated image development tool that allows photo editing and multiple presentation options for personal usage.
Seer - A Windows Quick Look Tool in Qt.
Eye of Gnome (eog) - Simple image viewer for the GNOME desktop.