Good start :) The only things I would say are: -Use some real world reference (can be anything, from computers, to machines, to small things such as bolts), so that it looks more functional and less like a bunch of shapes put together. -As mentioned before have a look at the other maps (spec/gloss), and have a go with…
I would just Google some maps..check out some that have normal, spec and diffuse to see where and how they apply their colors...I would also look at emission/glow maps for these types of textures. A gloss map would be good as well... Some good reference as well... http://www.hourences.com/…