Other geometric shapes can be made with a border print fabric in the same way as a square. The secret is to divide the shape into identical triangles. Create a template for that triangle (be sure to add the seam allowance), then cut as many triangles as you need from identical portions of the border print.
For detailed information on using border prints in many ways, download Making Magic with Border Prints Booklet.
Another great reference is Tips on Fussy Cutting Patches — another free download!