Well in general all of your pictures are missing a certain atmospheric feature. You really should put in some fog. And as has already been said, you need to vary the height a lot more.
Regarding the first pic: I think you should add in more of the small trees, as those seem to compliment the style of the buildings the most. I really like how the pink of the sky just rises above the far building, but I think it would look awesome if you added in a little fog, and found a way to lower the building, or raise the sky to expose more of the pink.
Second pic: Well regarding all of the last three pics, I think at least one other kind of tree is in order, currently it is far too monotonous. Specifically for the second one, I think that you should have the camp much less overgrown. The fact that there are towers built suggests that they would have enough time to at least clear out the area of most of the rubble and brush.
Third pic: Well first off I really think you should have set the time of day for that screenshot to midnight, as that would obviously fit the name 'night camp' much better. Other than that, all I can say is that I really do like the mountains, however I think you should choose different tile(s) for it. It looks a bit unatural in that sense to me.
Last pic: I personally think this one is the best done, but since it looks to be a civilian area, the guards and numerous stashes of weapons seem a bit irrelavent.
Overall, there are a few things in general you should work on (fog, height variation, etc.) but there are many things you are doing well. The sky for one. I can't honestly say that the sky looks bad in any one of them. | 
