Well, you need to practice mapping a little more (we'll see how much it gets better with time), because it's important to fill maps with stuff to make them look "less empty" (flowers, a tree here and there, or other stuff your tileset could have), or you could make smaller maps, if you want. Also, I've seen you've been using the tree tiles incorrectly (you've been using the ones that make it look as if there were empty space between them when you connect them, there's a tile to avoid that)
And, even when you like the floor that is used for the "fishing plataforms", then you'll find yourself in a lot of problems because that tile doesn't convine with anything (and you even put some flowers... that... definitely doesn't look good), if there's a tile you like, then you'll have to make an effort to make it look nice in the mapping.
Anyway, I wish you luck on your hack.
