XnView is a feature-rich, customizable media viewer that supports more than 400 formats. Includes batch image converter/renamer as well as basic transformations (rotate, filters, effects, colors, multi-page etc.). Various viewing settings include tabbed interface, fullscreen, slideshow, web page, contact sheet, image compare and filmstrip layout. Includes scanner support, screen capture, Photoshop’s 8bf plugins, image search, histogram, metadata viewer, automatic crop (deletes background), watermark, flash export and more. It can also store thumbnails to a temp folder rather than each image folder accessed, which is handy for portable use.
Alternatively, XnView Portable is pre-configured and automatically supports PDF interpreter/rendering engine Ghostscript Portable.