I've been doing maps for my own project, I've wanted my maps to stay close to the original style (eg. make them look like a Square map designer did them)
Here's some advice:
Some more scattered forests here and there couldn't hurt.
Perhaps some extra tress around and merging with the mountain range (look at the spots around Choras 1000 AD or Medina Village in the original game)
A castle ruins somewhere on the map is a must, it's in the tileset so why not use it?
Beyond that, take a really good look at the original maps of 600 and 1000 AD (since they use the same t'set) and just notice the detail and how it's setup, spend 15-20 minutes or so looking at them, taking in the detail-that should give you some kind of further inspiration.
If you want, you could send me a copy of the export and I could go to town, I wouldn't change much, more like detail what's already there.