Very nice render, and great models. I have only one suggestion; the floor of the bridge would probably be pretty dirty by vehicles and horses passing, so I would add a simple shape with a line of dirt through the center. I often do that if it's clearly visible. Just inisde the object, soft edged simple shape a bit longer than the bridge, with same location and rotation, taken through transform set to world, masking a surface shader (after the default shader), and pull some of the path dirt and stones in on the thus masked surface shader. Also through transform shader of course.