C&C please...............
Those may just be the biggest trees I've ever seen ;D I would suggest scaling them down by a factor of 10 or 20 at least.
Yossam I have to agree with Ryan. I think you could get a better 'clumps of woods' effect with a PF and displacement at this altitude. Your populations and altitude blends are convincingly broken up. Might be effective to get some mountain scale variations in those grey scree textures.
Shrank the trees, made some other minor changes.
The clouds Edge sharpness and density could come up a bit, and a touch lighter in colour, IMO, for a little more realism.
Much better now. Maybe you could try to increase the density of the trees a lot (reduce the object spacing) and add some PF in the coverage (set to 0.8 maybe) of your density shader to make the tree distribution a little more random (I think you already have a distribution shader to restrict the trees from growing in higher altitudes?!).
Something else: additionally to Wurby's suggestion try to increase the "roughness" value to maybe 2 in the cloud's density fractal under the density tab, while reducing the smallest scale of the density fractal from the default value of 10 to maybe 1 or even smaller to get more details in the clouds.
One more time...................
I like it!!
Dont know why, "Indiana Jones" comes into my mind.
The Aeroplane needs a bit of resizing i guess, depending on your focus: "Great flight action/plane with a cool background" vs. "A little plane over a great landscape".
Imagine a sepia-toned picture with post added dirt/irritations, incl. a nearer flying plane (more or less at same position, depending on the size).
It may look like an original pro-postcard/air-shot from "good old/better days".. :D
Nice render!