For a lock screen, I take a picture of the wife and I, customize it with a message to please call us if you find the IOS device, and include a phone number (using some photo editor, most recently Photoshop Elements). I then upload this as a photo to the IOS device, and select it as the lock screen. Now if the IOS device is lost and found by an honest person (there are some) they can call me and arrange recovery. For the dishonest ones, I use a lock code and have the device set to automatically erase after some number of incorrect entries.