Hi Cereb,
If you want to see DDS (DirectDrawSurface) files outside of Celestia, they can't be viewed with Windows Picture viewer or Paint, there is a handy thumbnail viewer free from NVidia (only220k) that integrates with the common task panel on the left of your window where you would see jpegs etc. in thumbnail view. Unfortunately it seems to have problems with 16k files, I use XNview
http://www.xnview.com which can show lots of file types, and in browser mode displays in a range of thumbnail sizes, and is a nice program to use, sadly it can't convert to DDS, but is only 2.67mb so is worth having as a viewer at least, hope this may help you,
regards Ziggy