The trees were described a couple of weeks back, they have had extra flock added to give variety of colour, and have been planted to create deliberate view blocks to the scene. Hopefully their placement will look natural, add visual interest, and by splitting the scenes may even make the layout appear bigger. A few more bushes and extra texture to the existing ones has helped too.
I have also given the track a couple of thin washes of muddy brown to tone down and colour both the sleepers and the ballast. The darker brown of the sleepers and the grey of the ballast still show through, but the overall tone is much more natural now.
Where the engine shed doesn't (yet) stand I have grassed over the end of the siding, and a large bush from rubberised horsehair and ground foam flock helps to disguise the end of the layout. This corner is barely visible from normal viewing angles anyway, so the engine shed can wait for another time. Anyway, I'm stuck for ideas as to what it should look like.
I think the result is that the greenery is less "flat" and is much more convincing than it had been, and the track blends it better. Next a few more details are in order.