Great work! I'm going to use Burj Khalifa in my mod The art looks amazing and I like the ingame effects as well.
You have to download a dds plugin for GIMP. Don't remember where I got mine; Google did the trick. As for which files: I just look around, e.g. for wonder art dimensions I looked at the work in this topic (PS: I have no access to my files atm, so can't check anything.)Do you know if there is a description/tutorial around here how to come from an image to the required .dds file? It would also be interesting to know which files are needed by a mod to be functional and their properties.