Well...this is an excellent work..i really like it and also like to know how to do it. you are free to don't expand your technics but...i think that a lof of people in world would like to know some of them!
I saw that other robot thing of yours (also 'ed it), and I almost not believe you when you say photoshop only..REALLY? this is the most awesome freehand or whatever this is?!? perfect kompositioning /w lights and 2d/typo..colors are brilliant and the details are nothing less than stunning. I know you don't need it, but here's a symbolic 8)