Here is a simple test trying to dial-in foliage populations. Still a long ways to go, but there is progress. Take note of the hill in the immediate background to the left. You can see the "glitter" of distant grass, similar to what is seen on grassy hills in the distance. I also screwed up on the clouds, but thats alright, as this was just a study.
The background itself is a simple star field. Nothing wrong with a few stars in the daytime sky :-)
Very minor postwork in PS. Slightly changed the contrast, added a tiny amount of sharpening, and that was about it.