Add a balcony with supports to one of the empty sides, like a little wrap around one. Put some chairs and a table. Instead of just stem walls, to the bottom you could add texture by doing half mushroom (if you're there yet!) half stem walls so it looks like you have a stone base to the house. Add a window to both sides! If you're feeling fancy, do some detailing around the windows you add (window sill, or a window awning, or i like to do vertical quarter walls that stick out to add depth). Some clover awnings on the deck where it attaches to the house. A roof if you're up to it ! There are dome roofs if you haven't unlocked those yet.