Firstly, like Pharaoh_ said, the water needs more depth. However, I think that the best thing to do here would be to just use the waterfall model for the water itself, like in
raid1000's Waterfall Castle. Secondly, I think that the lighting and atmosphere in the background is awesome, however, in the foreground, I think you could use some more depth. I find the best way to do this is to simply place a large glow/sunflare model right in front of the camera. It will do wonders for almost any terrain. Thirdly, the light in the windows of the building does not look quite realistic enough. I assume you are using glows placed behind the windows. In my experience it is best to also place some glows in front of the windows. This makes the lighting look like it is coming out of the building, rather than just sopping at the windows. Fourthly, some of the textures on the rocks in the foreground are seriously stretched. I would recommend replacing some of them with several smaller rocks. Fifthly, I don't really think the adobe building on the left fits in very well. Perhaps you could simply try using the other adobe model? Finally, while I like how you created the "grass" I find that it is a bit flat in some areas, particularly on the right, and could either use some height variation, or a few more trees to just cover it up. Furthermore, I don't like how it sticks over the edges of the cliffs, but I can't think of an immediate solution for that other than just making it smaller and/or covering it up.