Looks great! You could really take off with this concept. You could try making the pyramids more like mirrors; not pure mirrors, but like a chrome or something, that way we'd see reflections in all directions (this will, of course, increase rendering time). You could repeat the structure a few times in random places off in the distance, suggesting that there are "parks" where Earth still comes through. You could scale down the terrain, perhaps making it look more like real mountains, forest, etc. Maybe even water? Another suggestion: I like the sunlight, but this might call for a bit more moody of an atmosphere. A bit darker. Anyway, I don't want to seem like I'm designing your piece :-) It just gets my imagination going. Happy rendering!