Thanks Bjoern! It isn't that difficult though. In fact I just start with a 128,128,128 layer, putting a layer of darker panellines above that layer (so they appear deeper) and lighter rivets. Then, I add a metal effect: take a regular water texture, desaturate it and adjust the contrast+brightness so that it's around 128,128,128. Using a layer mask, I mask the panellines and the rivets from this 'water' Next on a very slight noise overlay and that's it (for metal, fabric is another thing). Oh, and convert it using Arno's MCX Texture Converter.
Edit:
Fabric: I have normally for these textures already a black-to-alpha blend, which I take along to the normal map. The mid of the fabric is being darkened using a black airbrush and regulating the opacity. A white stripe is placed over the stringers, that's it. It's already very satisfying after a few trials.