That's interesting! As a lot of people said, tileset are interesting. I want also to praise palettes (colors) choice: it exalts all the scenery, keeping the brillant colors from Ds (lite?), which I personally love. There's only a little thing to say, there are some empty spaces in maps. You can use differente grass tiles to make it more various.
And one last thing (XD, sorry): you are using a lot of different enviroment tiles also in the first map, try to take something off, like those terrain rocks, mushrooms or deep water. It'll be better to see them into other maps, to keep "new things" for the other maps