yes you should. why do you use a sun with an -90deg angle? No long shadows or at least shadows at all. Maybe a small angle would be good to give everything a more interesting look. Besides you should try to use more displacement geometry outside the "camp" and with more variation, it looks kinda odd to me if the camp is inside everything.
Maybe you can use a third displacement texture as well to vary the ground a bit more.
Here is my work (again), i hope you guys are now a bit more pleased with the background. I sill need to work with the random window lighting, but i think the way is right. Especially if you don't forget that only the roof of these 3 buildings are the playground for the big kids. Everything else is only there to look good.
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[Blocked Image: http://cloud.steampowered.com/ugc/577806319637194916/62D00117307DC8C47CA975A8914C64FFA1774649/]
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[Blocked Image: http://cloud.steampowered.com/ugc/577806319637195874/47CC4873138E6D177AB65ECC7A9FE18679C23539/]