Fragment - A powerful image viewing suite with advanced metadata info
Okular - Okular is a universal document viewer based developed by KDE.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
ImageGlass - You can use Image to view your digital images and photos of many different formats.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.