There's a lot of nice stuff going on here, I especially love the colors. Now, I'm not picking on this picture, but since it's finished, I can point out a lot of stuff since I know it won't be addressed later in the process.
1- the composition is segmented into parts. Instead of being separated into a 1, 2, 3 read- each quarter is equally important, therefor nothing is important. I scaled up the guys so that either they could be the focus, or the foreground element secondary read, right now they're just tacked on at the bottom. Also, overlapping shapes helps with depth more than atmospheric perspective ever could. The overlapping also helps in the other elements, like not making the mountains follow the countour of hte building, that just looks too convenient aka fake. It's natural for us to want to do that, keep elements out of each others way, but nature doesn't adhere to composition.
2- the scale in your actual design is all over the place. You've got a little window with a windowsill, then an inch down, there's tiny trucks, it throws the viewer way off. Watch your scale cues, not just putting objects in for scale, but also minding the type of construction and its functionality at various scales.
3- that antenna shooting a laser, besides being too distracting to be in the corner, or too cornered to be a focal point, has more scale issues of its own. It's huge in scale, but in design looks more like an old tv antenna. Watch where you get your reference.
4- everything needs to be based in reality, and some of your architecture is just nonsense. That weird floating building with posts coming out of it, not only does it look like its a small room up there when in fact its a giant hanger size warehouse, but it's just floating on two posts. Ever seen a table even do that? Let alone a giant building?
Hope that helps!
