From the sky to below is quite a change. Personally I think a dungeon is easiest to start with, because it has clear edges for the mapset (rocks are better for a mapset edge than trees, in my opinion). The idea is still on my list of future maps, so maybe one day...
The map you made looks good so far, like Cleo said.
You might want to run the map validator/checker script to see what is not allowed by the server and fix it. Some mobs seem to be outside of spawn point, some quest markers outside of mobs. Running the map validator/checker will discover these bugs and tell you how to solve them. There is a strange object underneath the peasant in the old woman's house, what is it and what does it do?
Some suggestions for improvement: You should add some light sources (i.e. lamps, torches..) to your underground city, under the surface it's usually dark. You could add some pottery to the old woman's house, a library to the mage's, tables and tapestries in the castle, a scarecrow to the farm fields, some plants on the grass. Maybe some statues, be creative when adding details. Such aesthetics make the map unique and interesting to explore. You could even replant the trees so they're not in a straight line and maybe do the same with the dungeon edge, you might discover a tunnel to a new hunting cave when you do that. ~Kiana~