Not bad of a start, but you suffer greatly from ESS (Empty Space Syndrome). :> For the interior, one way to get around it is to make the room smaller, and put some shapes into it. (By the way, you can use the autotiles to put a top on walls, if you didn't already know that.)
For the exterior, there are a lot of empty spaces as well - perhaps you can manipulate the fences so they have some odd shape that fits into some of the spaces. And try to break that hill from being shaped as a square, to look more natural. More details, before things get clustered, is always good.
Keep it up, you'll get there! :>