Wow, coolness! Your M&S entry is hilarious, and I really like the direction you’re headed in with the second piece ~ definitely continue to work on it!
I do think that the rendering could be a bit tighter on both pieces. I know how much effort it must take to get them to level at which they’re at right now, but I feel that they could be rendered even more tightly for that illusionistic effect.
Also, you might want to soften some of your edges. They seem a bit to have the same consistency and feel, and what’s nice about the painting medium (digital here) is that you can do so much in terms of varying soft and hard edges. I tend to go TOO blurry in my images (just a personal preference, I guess), but I think in your pieces, some of the items which are farther back in the picture plane could stand to be blurred a bit, and given an atmospheric (bluish) hue.
Good luck with the second piece ~ please continue to post your WIP!
Thanks for the posts!
EDIT: The robot’s expression is awesome!