For example, this picture of Elon Musk and Grimes at the Met Gala functions well as a custom Zoom background because your head, which will generally be sitting in the middle of the frame, doesn't cover up either person.
If you're seeking the custom background of your dreams, you should find images that don't have a lot going on in the middle. If you want it to be a picture of someone, don't pick a headshot – pick two people standing next to each other, like Musk and Grimes.
Or, continue on for some images that are tried and true Zoom masterpieces.