Fladdermasken already mentioned the important things to change, there are also some additions. Since it is an Orc-City there should be stuff lying around and there should be other and smaller buldings as well. Maybe some Npc-Orc would make it more vivid. Also some more variation in the background (trees), maybe a mountain or so.
Regarding the last picture: bad grass spamming, less is often more. You should use ANOTHER TILESET.
I also dont like the structure, but thats kind of a personal thing.
Keep it up, your terrain got potential!!!
Somehow Orc-Encampment picture doesn´t show up...