digiKam - Professional Photo Management with the Power of Open Source
Fragment - A powerful image viewing suite with advanced metadata info
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
ImageGlass - You can use Image to view your digital images and photos of many different formats.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
IrfanView - IrfanView ... one of the most popular viewers worldwide.