My new favorite thing to look for at online markeplaces is photos of people trying to sell their mirrors. Many people find hilariously awkward ways to hide their own reflection while taking a photo of the mirror. Other people simply accept the fact that they're going to be in the photo, too.
This video compilation shows some of the funniest mirror photos from online second hand sellers. My favorite photo is one where the seller has completely covered themselves in a giant blanket like a ghost. Only their hand is sticking out to take the photo.
In another great one, a man decides to band over with his butt facing the mirror to obscure his face, and takes a photo through his legs. One of the photos near the very end shows someone fully hiding behind a door in front of a mirror, with only their arm and camera phone peeking out through the door crack to take the photo. There doesn't seem to be one perfect way to obscure one's identity in a mirror-selling photo, but all these people gave it their best shot.