Auntie always said that you have an exquisite taste! Improving your farm will also let you decorate your house as you want.
You will find various furniture and decorative elements for walls and floors in the store. Some of them can be bought for Green Bucks, while others, especially rare, will require Gold Coins.
The higher your level, the more items are available to you.
And yes, these decorations are not purely cosmetic. When buying furniture, you also increase the number of your Points of Comfort.