hey Urgwaine,
that's very good work, and you seem to have mastered many elements of design.
Some comments from me in good will:
+ you could work a bit on the land, placing different types using brush #1 and see how it varies.
+ nice work on the bridge, but in order to get rid of the hole on top of Thor's Hammer, you could try placing another Thor's hammer on top, but tilted sideways to see if it looks better. Or if you don't like that, you could place 2 Thor's Hammer Heads tilted the opposite way and overlapping each other. I know it's hard and long work, but you seem to be a hardworker anyways.
+ you could try and roughening up the terrain a bit more, unless you prefer it to be flat.
ehmmm, that's all I guess...
regards and keep up the good work
the Elder
"imagination is more important than knowledge."
Albert Einstein