I don't like the trees, why didn't you use the UTM?
1. More different tiles
2. End of the World-Try covering it with more hills, like 2-3 layers of hills.
3. The hill on the left, you should lower it, it looks really unnatural.
4. If your keeping the trees then at least lower them down by clicking "Ctrl+Page down"
5. River rushes can sometimes look really bad if not used in the right way so try using more shrubs but shrink them down in hight by clicking on them and "Page down".
6. What's up with the portal? Looks really weird.