Full Display with upcoming calls

Try to open the Contact app and find one of the contacts that does not have a Fullscreen Call Image. Open the Contact and tap Edit. Tap on the image and select the same image at the bottom of the overview. Then tap Edit and customize the image and save again. I can get some of my images to change to Full Screen that way. But I often find that it is the vertical images that fill the screen.

EDIT:

Just tested it. If I create a new contact and at the same time take a vertical picture and use it as a contact picture. The image will then be displayed in Full Screen.

If the photo used as a contact photo is taken "Vertically" - then my experience is that it will fill the entire screen when you receive a call from that contact. But if the image is scaled, or square, it will be displayed at the top next to the name, as a small round image.

You're welcome.