You've only seen it in photos, never in real life? So where are you getting the photos from? It's hardly a prominent feature of them, so I think it unlikely that you'd find these unless either it's very common or the photos are tagged in some way that identifies this icon as a feature of the photo, and I don't think this is common (your threads are the only place I've ever seen this, and nobody else is able to identify it either). So how are you finding these images, because that seems the best lead you have on what it is?