I don't think I have time to work on this with you, but I can at least provide some useful info (particularly to SpiralOut). File format is .dds, Photoshop exports to it natively I believe and Gimp has a free plugin. When exporting make sure there is only one layer with transparency, and that the layer size is the same as the image size. The shorthand for the colors I believe is R8G8B8A8. The icons themselves will probably be completely white, save a slight drop shadow perhaps (something around x=0, y=2, radius=3, transparency=50). Sizes start at 256x256 for basically everything in the game, and I believe you need the following sizes as well: 200, 80, 64, 50, 48, 44, 36, 30, 22. For an example of what the dds files for the base game look like, ask kantorr to give you the following image from the pantry: Steam\SteamApps\common\Sid Meier's Civilization VI SDK Assets\pantry\Textures\CivSymbols256.dds
(protip: the files can be in any size you want, really, you don't have to have yours at 2048x2048 if you don't need to, all of mine are just the one icon at 256x256, but you can combine multiple icons into one image)
