
-you could use atmospherical perspective on the far away horizon to liven up the scene
-you could apply more perspective to the trees
-you could give the battlements a portruded profile
-the contrast of the stones on the top is too much. Introduce another color which ties it together to a single plane
-the front merlons are perspectivically seen to small for the side merlons, move them in the middle
-get rid of that double pixel black line in the stone bricks at the frontplane of the tower
just out of curiosity: is there any specific system you are doing this for or are there any restrictions you set for yourself?