Mere geometric shapes do not qualify for copyright protection. "it is not possible to copyright common geometric figures or shapes such as the hexagon or the ellipse, a standard symbol such as an arrow or a five-pointed star." See the Copyright Office's Compendium of copyright registration standards, Section 503.02(a). Geometric shapes considered "unoriginal" under this test can also include more complex but historically-common designs such as the "fleur-de-lis." See Forstmann Woolen Co. v. J.W. Mays, 89 F.Supp. 964 (E.D.N.Y. 1950) ("Surely and certainly in the form in which the fleur-de-lis are shown, no originality is displayed"). As a result, even some well-known images such as the New Orleans Saints' logo are not subject to copyright protection.
These types of simple logos are considered "public domain," meaning that anyone can use them – although the way that people can use a public domain logo would still be limited by trademark law.