Specular or roughness map, would help too since you get a lot of realistic effect with different materials reflecting differently. But it can conflict (look weird) with normal map if these are not well balanced. So in some case you better off with just speculars.
You should take a look at the Mig29 maps. These are perfectly made mapping IMO, though you might need the 'compressonator' program to view some of it.
