Nice image Mark
I like the displacements as they are. I was thinking you might try to add a(n extra) strata shader to give some nice layering effects.
Maybe you can try settings similar to these:
steepness : build up ~ 1 : 1.5
depth : spacing ~ 1.25 : 2
If you then create 2 strata shaders with slightly different tilt directions and angles (20 deg differences for example) and then mix them you can get really cool results. Instead of mixing you can also break one up using a high contrast powerfractal and invert that breakup for the other strata shader.
Furthermore I like the use of large fake stones. Perhaps in the future you can try to add some extra displacements and texturing to them to make them look a bit more different from the overall terrain colors.
I think your work is really improving fast, looking forward to see your next, it's a joy
Cheers,
Martin