Turning on your camera in a Kemble Circle room or call, or in a Kemble Work Link, shows a preview with your background choices first, and nothing is sent until you press Turn on camera. Don’t show this again turns it off on that device. Add your own takes a PNG, JPEG or WebP picture of up to 10 MB, scales it on your device and keeps it there — it is never uploaded.
In a call, the arrows beside the camera and the microphone switch between your devices without leaving. A Link’s More menu can hide your own picture from your screen while your camera keeps sending.