Garden Accessory
A garden accessory can be any of a wide range of things. In general, the term accessory is used to imply something that isn't necessary. There are a lot of great examples of such items in garden supply which are not needed but serve to enhance the outdoor area.
A sculpture is a great choice for a garden accessory. One that is large and uniquely colored can stand out as a focal point in an area which has become too dull. Some may double as fountains, which can provide more energy and encourage more wildlife to visit the space.
Other garden accessory items may have a more subtle design. Edging or lights can be great examples of this. When used well, they will work to create a harmony which ties the overall appearance of the outdoor area together.