Much more than an afterthought, garden ornaments can guide how you shape and use your outdoor space, and affect how it feels when you’re in it. A wrought-iron gate can mark the entrance to a world of green, a tree-hung lantern raise your perspective, a curved bench inspire a nap. Carefully placed, pretty yet practical, these elements offer subtle but effective clues: Turn here. Look up. Slow down. They also give a garden space a finished look in all four seasons. The trick is to not overdo it.