I wrestled with this for a bit; it's an actual dungeon and not a scene, so it's going to have enemy encounter NPCs and such. I've noticed that when a game has enemy sprites as opposed to random encounters, you pretty much have to have an appreciable amount of empty space, or the luxury of being able to avoid encounters is lost.

Also, the fort spires are supposed to be peppered throughout the map. It'll make sense once you explore it. Think of it less of a setpiece and more of just a piece of a larger map meant for exploration. The palette of the tree might change a bit for the final version though.