I guess my only crit would be the eyeline as she is looking right above the head. Which sort of directs the viewers attention away from what you want them to focus on. If there is something that she is looking at beyond the robot then for the concept to feel complete you should give the viewer something that they can look at too. Or they may just assume its a mistake in the painting. Other then that I think the concept was well thought out and you did a great job on lighting and character build up.
As I am looking at it again I can see that maybe her thighs needs a little more defining.
ha ha but you don't have to take my word for it as your better at layouts then I am.