Once Conference Room Display is turned on, you can customize the way it looks.
Go to Settings on Apple TV.
Go to AirPlay and HomeKit > Conference Room Display, then do any of the following:
Display a custom message: Select Custom Message, then enter the message you want to display. (Your message appears only when Apple TV is in Conference Room Display mode.)
Set a photo background: Choose Select Photo, then choose Albums to pick a photo from your iCloud photo library.
Require a PIN for AirPlay: Select Require PIN Every Time to turn it on.
Anyone who wants to stream to your Apple TV while it’s in conference display mode is prompted to enter a 4-digit PIN shown on Apple TV.
See a preview of Conference Room Display: Select Preview. To exit preview mode, press or on your remote.