I work with both Photoshop 7.0 and Illustrator 10.0 and find that I prefer to use Illustrator to design to this point. Creating a simple black/white gradation pattern with the hues fluctuating throughout the gradation will give a metallic look. This advice may change as the map I am currently working on is MY first (and am creating it through Illustrator mostly) but it will also be three dimensional (foam core overpass and a steel girder building!).............I'm putting alot of time into it and I hope it pays off! I'll see if I can post some pictures when (if) I finish it.