The three-tile high walls should be four-tile high as to retain the height consistency. It is a common problem for mappers, so don't worry much about it.
I added in a few tress and bushes with this one. The thing I'm not-quite-certain of is that one place near the top of the map where the side of the left-cliff meets with the walkable-cliff.
Sorry. I know which section of the map I'm talking about, but trying to explain where this is seems to be escaping me.