The concept as is is really good, but needs some polish.
The first thing i noticed was the purple colors. They are just kinda there. If you were going for decals, kind of like it was painted on there, then i would have grunged it up a bit with the rest of the head. But if they are like power lights or something, a glow would really help make that clear.
The shading depth could really help this head as well. It's like there is a constant of the same type of shading all over the head and no variety. Certain areas could be darker to give the illusion that it's further back and deeper into the head, and certain parts could be lighter to give the opposite effect.
The back is kind of boring and so is the front, but the sides are a bit cluttered. I think the reason this is is because you made the plates of the back and front too big and the ones on the side too small. This can be easily avoided by double checking your sketch on a globe to make sure the mapping is right. A good thing to think about next time i suppose.
As is now, you could add some light purple decals like war stripes or more lights to fix those areas.