I really like the trees. I'm going to try it out and play around with it in my current project. I think they look a little too blobby and blurred in some places.

The coast line could use some smoothing in some places but also some fine detailing in others. If you got the layers set up nicely tou should just be able to go over it with a fine hard edged eraser.

I'm my self trying to learn the art of ground relief and you done a good job, better than mine!

You should add some texture to the gound thou. Maybe some sandy shore, cliffs, muddy areas or different hues of grass.