You should add... ummm, FLOWERS?
Well, you also need a reason for the little blocks that seem to be covered by grass. They are usually part of an old path of some kind. But there is no pattern of a path there. ;x
Hmm, you need more weeds and mabey some swamp
And the NPC Trees are fine. They allow you to pass by the tree in the back so it looks more realistic. The Full NPC Tree is useful for making a few trees go together
Raiting: 8/10
Nice level