Your lines are so good, and your grayscales are awesome! I think you should try to do more dynamic things in them though, like figures flying through them, machines racing/being blown up or something, so that they're not as quiet and 'empty' y'know?
These quick ones are really great, very nice quality in great speed. Maybe a very limited amount of white could offer some more contrast to the focal point and offer the illusion of a wider value range, but ok not sure, i love the composition as it works now.
Keep up the great work!!!