The water depth fade doesn't work on ortho view, which basically makes water practically invisible. Notice the house which is 75% submerged appears completely above water. A water opacity scale might be a good idea.
The map maker also takes a screenshot including the entire window which seems unnecessary and adds to file size.
Another thing is the fog only affects the environment which makes the edge of the map in free roam very visible.
There are a some other things like the ability to add/import more models or terrain sculpting but I get the feeling those are being worked on already or maybe you don't have those in mind since I noticed the description implied this was more of a casual app. Either way, it's an extremely powerful tool and you did a very good job with it.