That is coooool.
Hm, lets see... There's a really nice variety to the lineart thickness, but I would say it could you a liiittle bit more at the hand closest to the viewer, just because I love me some thick lines.
Somethings up with the girls body, though I can't quite pinpoint it. Perhaps her torso is too long or something?
The massive amounts of lines on the robot-monster thingy really draws the eye towards it. That may be intentional, but if you want to make it a bit more balanced picture, consider drawing some more details on the left part it. Perhaps some background or some accessories on her person. Especially the last one, I think, just a bikini seems a bit plain compared to the detailed monster-robot.
I luuuv all the cool details on him, though. The shoulders seem a bit asymmetrical, though. Shouldn't there be a little spike on his right one, too? As well as some of the shapes on it seems to be different.