In this tutorial you will adjust or add photos to contact to full screen incoming calls view

Actually sometimes this method will not work with you
So try these methods:

1. Take a screenshot of the photo and the adjust it to contact
2. Turn off iCloud photos sync
3. Turn off Contact sync to iCloud
4. Try to use photos that taken from your iPhone camera
5. Try to delete the contact and add it again then adjust the photo
6. Let your friends keep calling you multiple time, sometimes…