Have you ever thought of using ModTerrain bricks that come default with Blockland?
Getting some hills in a build like this would also help.
Right now, it is a very green plains with equally green structures.
Even though there is something on the field of another color, it would help if you tried mixing up some more colors (and/by adding more detail) in your build then only a lot of green.
As for the trees, put them where you think there should be trees, or where it is a bit too empty in comparison with the rest.
Don't put a big bunch of them in one tiny spot, space them out a bit.
I am not the best builder, but i don't have to be the best one to give you some of my opinions and ideas about it. :)