Marisa-
Thanks for doing all those thumbnails, booyah!
Just a few crits for you to think about. Your images are lacking any real perspective. Most of the images below only had parallel lines running flat across the surface, they never converge anywhere and this makes it difficult to get any depth into an image. No matter how crazy your atomosphere is without any hints at where a vanishing point may be will just flatten your images to hell and back. :)
On your first image you created for this series you hinted at some perspective on the bottom bridge but didn't really follow through with the rest of the structures. Any perspective that is there is very timid, so I recommend pushing some of these elements like i did in a mini-paintover. All i did was copy and paste your brushstrokes and warped them enough to guide the eye.
The last image you did below has some great atomosphere but again no real perspective cues. Even just throwing in a ground plane via copying your whole image and warping it into perspective can help guide the eye through the image. Also, amp up that little satellite thingie you got going on, go big or go home! :)
Thanks-
Levi

Bongo Bong.