You can also pick some classic furniture pieces and arrange them perfectly around an outdoor fireplace mantel to give a complete look to the yard.
Apart from the aforementioned ideas, you can have a waterfall, pool, pond, or a well for a perfect backyard. Also, don't forget to add proper lighting to the art pieces. You can also try making some simple crafts and have them installed. Points like placement of the art piece, its material, and size need to be considered while finalizing them.