Looking for a free image viewer? Perhaps ForceVision would suit your fancy.
It supports over fifty different file formats, conversions, transitions, and allows you to bork with the images with thirty plus filters. It even provides a slideshow feature, full screen mode, and thumbnail mode. You can also do file associations with the types of graphic extensions.
I personally don’t use this mainly because there are other products that I’ve grown accustomed to but don’t let that stop you. If you’re looking for something new or never had an image viewer, perhaps this is your holy grail for image viewers.