Hey there! It would help if i could get some closer pictures of the map but here is some general advice:
Add bushes of varying colour, size and quantity
Add rocks of varying colour, size and quantity
Add grass of varying colour, size and quantity
Overall add lots of foliage. One of the things i do is add some foliage beneath every tree as it adds a lot more detail to the ground and the tree. Also combining rocks, grass and bushes into a sort of mound can add a fair amount of detail.
Your trees look nice and varied but i suggest you mess around with either the sizes a bit more and have some trees which really stick out with a lot of detail around them or add different types/forms of trees.
For an example of a few things which i mean here is a scene im in the progress of making and getting feedback for: