For filling up the emptiness, try adding country borders, cities, towns, roads, dungeons sites, labels for things like Spooky Forest, Big Arse Mtns, River of Blue Water, etc. Colors look nice, all in all pretty nice. Only 3 things I might fiddle with: break up the forest outline a little...looks kind of orderly; add some brown to the mountains, and add some variation of color to the grass (lighter green for higher land and darker green for lower, maybe some yellow or tan splotches for plains). Like I said, looks pretty nice so keep up the good stuff.