Hey there. I really dig these pieces. Very well rendered and balanced. My only real problem with both pieces is that they lack a large range in values. Mainly, i think you should have DARK colors not only in the background to anchor the image, but also throughout the image in order to make it Pop and seem more plausible. Also, I like the dark coloring underneath the spacecraft, but on the android thing i think the dark is too much, enveloping the form rather than accentuating it. Anyway, these are just my two cents, I really like them and hope to see more of your work.
Disclaimer: Unless otherwise stated, I have no idea what I'm talking about.