Sundials are a nice touch. I have a small windmill and old wagon wheel among my prairie plants. Such artifacts serve three purposes. Like the frame idea, people will accept that which they know is intentional as they will reject the same thing if it appears random. Second, such artifacts lend a sense of welcome to people.
Natural landscapes are less threatening if they contain inviting human touches.
These touches do not, however, detract from the natural landscape's purpose of providing habitat for native species, and working with, rather than against, Nature. It is pleasant indeed to sit on a bench from which one can watch the butterflies nectar on the Coneflower or the Goldfinch drink from the Cupplant.