Image viewers on Linux has an article on image viewers on Linux. It mentions a few alternatives to the usual digiKam and F-Spot (GQView and Picasa), but one that looks really interesting is imgSeek. It is mainly focussed on searching (including searching by similarity of images - not sure how nicely this will work but the concept is great) so it does not have image editing capability, but as I am after a good tool for organising images then that suits me fine.