Looking good so far. Are you using 4.6 yet? It would let you automatically generate lighting for all those emissive surfaces you have. My main crit at this point would be that the scene feels generic because you need to add some elements that tell a story. I don’t know exactly where you want to go with this, but I would recommend putting some time into making a few decals and perhaps coming up with some other ways to put across a story here. I seem to remember that you wanted the bottom areas to be covered by sand, but it looks like rock/dirt, not sand. I would stick with the sand idea, start putting in some background elements, spice up the lighting, add vertex colored sand to your master materials, and add some more color to the environment or at least some more sense of what this place is.
Sorry that’s kinda all over the place, but I hope it helps.
PS: Dusk is never a bad thing in video games… 
EDIT: After looking at your screenshots again, I think the best thing you can do for instant results is to add lighting for the emissive areas. It will make your scene pop so much more…