The design is fine, it looks well thought out, although visually it needs some work. Its understandable though; not everyone is a talented cartographer, spends a lot of time on it, and is as picky as i am with maps.
As for the mountains, they could present a pretty glaring problem aesthetically when you try to draw in the empires, since the mountains are anti-aliased. What that means is its not just made out of black pixels, there are many shades of grey that help it transition to white to make it look visually appealing. The problem is, what if an empire's color is Green. The mountains are anti-aliased to transition to white, not green, so the grey pixels would stand out and make it look odd. Not a huge deal, but the little things set people off, especially in NESing.
There aren't too many mountains, i suppose you can fix them if you wish to. If you want a mountain that isn't anti-aliased, take a look at the map on the front page of my NES (its in my signature, and the map is in a spoiler if you can't locate it; I didn't make those mountains, but its just the easiest path to them i could offer you) You just copy and paste them around each other to form mountain chains and they look a bit better visually.
It may be too late for these changes, but just keep that in mind for your next NES. I think a map is one of the most important parts, and can make it a lot of fun!
