Picaxo is a lightweight image viewer inspired by Irfanview. Although it is being developed on Linux (natively on Kubuntu 7.04), its primary objective is to be platform-independent. Hence why Picaxo is being developed in C using the SDL library.
A feature of Picaxo that is not so common in image viewers is that it can view images not only on your filesystem, but also on the web. Instead of a filename, you can pass a URL as a parameter and Picaxo will download and display the image. Now this network functionality works even on Windows!