All very good advices! Thanks!

Here is an updated version.
I did work on the rocks and added the shadows... I also tried to add some patches of grass in the middle of the road but was not really happy as to how they turned out and removed them...

I also worked on my rock face through another approach (basically, sticking some bits of mountains I stole from dundjinni) and I think it looks better, although I can't seem to be able to get the shadows to work to add a real feeling of depth to it...

Click image for larger version. 

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