Sooooo Whimsical! Deciding factor # 1 - Size. How does it measure-up for the intended purpose? Does it need a border to reach the intended size? Deciding factor # 2. What color/s? Not as easy as factor #1. With such a cute top, a sparkle, or mini border would set the top into a neat frame before applying the border to achieve the size necessary. Your choices are almost limitless. The piano key would be ideal.
It's already a show stopper. Kudos.