Slightly darkened the colour of the middle ground hills
Slightly lightened the highlights of the middle ground hills
Got the shading a bit more even in the shadow areas
Hidden the pencil outlines, which can still be seen slightly from an acute angle
I guess this is one of the reasons why we never stop painting - we always know there is something more to learn, and the next one will be that much better for it.
I'm still having trouble getting good photos of my acrylics. For this one I tried fiddling with the white balance, ending up with the setting for natural light under cloud. Then I tweaked the brightness and contrast in Gimp, slightly reducing contrast and increasing brightness. The result is reasonably close to the original, but not perfect.