This is something that I've been going over for a while started in Terragen and have moved it over to T2, import heightfield of main piece added another in distance, painted shader on top for population of trees and another for some stones at bottom around small pool of water. Not sure what else to do, messing around tonight I nearly lost the things I liked about it but got it back to a degree.
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What is the haze setting of your atmosphere? It seems to washed out. Also some power fractals on the cliffs would help. Use lateral displacements. A compute normal connected to the input of the power fractal will be necessary. The compute normal is easy to add in the shaders node network.
Haze setting are Density 1.5 exp height 3000 glow amount 1 glow power 1.25
Can the landscape be scaled smaller using a height field operator? You'd have to adjust the camera afterwards, but it might get rid of the washed out look. Try reducing the haze density first, maybe 0.6 would work.
Been doing work on this for a while trying this and that some successful and others not so,happy with this result and time to move onto something else. Had to do a few crop renders and stitch them together in photoshop to improve and fix somethings that weren't working on my full render. used Lamposts grass there, I did have some longer grass mixed in but for some reason this 2nd grass object pop was floating about a foot off the ground but despite amending height between 0 and -50 it wouldn't move down even though the bounding box would move up and down.
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full size
http://private-tee.deviantart.com/art/Ridge-129020893
this one is really good...
...except the fake stones you have to work on their color and displacement...
The fake stones needs a power fractal using a lateral displacement. A compute normal needs to be connected to the power fractals input.
Well the fake stones layers have a power fractal attached to them and I made them the same colour as the main rock, idea being they were once part of that rock and have fallen at the base.