Jon Swanson has light skin and dark chocolate hair, which he appears to have combed like his father, Ron Swanson. From the photograph seen in One Last Ride, he seems to have dimples. He has steel blue eyes.
From the few appearances he makes, we know a surprising amount about him. In The Wall, we see that Ron has taken him to the abandoned floor of City Hall. Unlike most normal babies, Jon doesn't cry, fuss, or get scared when around power tools. The loud noises don't bother him, and in fact, he looks like he's enjoying it. This shows that like his father, he enjoys construction. Another similarity between him and his father is that from the shown picture, he likes woodworking.