Yes, one of the greatest challenges for me is the transition from model based to procedural for small object populations (grass or small shrub sized) for scenes like this. Just getting the colors right is really tough. I think you are absolutely right on the displacement needing to be associated with the colors/textures to boost realism. What I would also suggest is that there is seldom an area of large trees and low grass only (even in pastures). There are plants that livestock will not eat, there are dead trees, thorny shrubs, rocks, etc. Maybe man-made features, like fences, walls, ditches. Animals create their own paths which are discernible from above. Just lots of variety in general. The higher the resolution the more of these 'small' things are needed for realism's sake.
That village is looking really nice I must say. Good stuff!
