Now though looking at it to try to determine what can be improved:
First I see a possible problem with some textures. look at the stone texture of the obelisks then look at the store texture of the building and the stone pavement. On the obelisk it is fine grained and the details are sharp. On the building and pavement the scale of the stone's details are too large and blurry. The would imply that the texture map for the diffuse attribute that you used for that stone is too low a resolution and the details are being smeared during rendering. (I posted a tutorial for the workshops at Dave So2 it is not available now since he canceled that project, someday I will rework that tutorial and upload it. For now I will email you a copy of the illustration that shows the difference cause by texture resolution.)
The same is true for the sand/dirt texture on the ground.
The building looks a little too shiny, the dust and grime that should be covering it should make it look more dull.
The shadows look too dark. To fix that render two copies of the picture one with shadows and the other without shadows. Load them as two layers in your paint program and blend the two together, fading the top layer until the shadows look more normal. The scattered sunlight from reemission from the atomosphere would prevent such dark shadows during the time of day that the angle of the shadows imply.
The shadows cast by the riding animals are a little strange, the other shadows are long like maybe about 5 P.M. but the shadows from the animals are shorter like from about 1 P.M.
It seems that there is something unusual with the camera settings, there is some fisheye lens effect.
For a realism, the colors are too saturated. You could try lightly desaturating the picture during post work.
I hope this helps.
Pangor
I know I sound like a fanatic but I like doing postwork since I do them a lot on photograph so I like renders that looks like photograph, maybe not photorealistic but photographic.
