It's intended to be a head badge. A head badge is the decoration on the front of the head tube of a bicycle. Some head badges are simply paint, but others are raised decals or even metal. I believe this one is intended to represent more of a metallic 3-d head badge, with the color of the heart matching the background color to give an impression that it might be a cut-out, which is a common design element on head badges.
The original design idea had a heart logo with a bicycle in it:
Design for Bicycles Stack Exchange.
However, some people didn't care for the heart logo. A headbadge was suggested by zenbike and others.
The final design had a headbadge with a heart in it: New Design Launched
Here's a larger version: