Maybe you should make your maps smaller, and more detailed. I'm not good at mapping, but at least, i think i am not that bad also, and you might learn something...
(Do smaller maps, and not so many empty space. Also, add border tileset, so it doesn't seem like you can change map by going in any direction.)
Here it is something made fast up , only to give some example, of something that should look at least alright...
Actually, my interior is also way empty, but with 1 or 2 NPCS around would make it good thought...
This forest map, i think it gets prettier, than, big map, with 5 trees, alot of empty space.
That's some tips thought...Anything i can help, i try to do.
Hope i could be usefully