If you're looking for Graphic Converter or even iPhoto, then you might be disappointed. If you're looking for an image browser that is fast and easy to use by keyboard and mouse, then I think that this ImageBrowser works very nicely.
Many other image viewers are rather clunky on my 600 MHz computer, but this has some nice basic features (scrollable thumbnail drawer and slide show) and the ability to scroll through all image files in a directory by using left/right arrows, or Command-N. Also, the up/down arrow keys rotate the images. I like it.
I think this guy also wrote a perl script to find the WAN address from a router (which I modified to work with my router). If you like the other ImageBrowser, use it.