I have tried that but the computer wants to save it as a new file automatically I can't do anything. The only way to solve this problem is to find a program which allows you to open and save files in DDS format. If you go to models folder in the data folder, you can find inside the textures folder some DDS file like the sandard senate or other. If I had a program which let me save files in DDS format I could change for instance the legions standard putting down something a bit more historical or maybe also something funny like " We, Romans hate Germans; They stink too much!