Chances are, your lost smartphone screen will look like this to whoever finds it. (If your phone is not password protected do that now.)
This presents a problem to the good Samaritan who finds it. They don’t know to whom the lost smartphone should be returned.
Sure, you could call the phone and hope they answer, or try using the ‘find my phone feature’, but that takes time and a positive result is iffy.
Give the finder a helpful clue as to who you are. Customize your background wallpaper to include some information about you.
Including an email address is a very good start. Now they know how to contact you. If you want to keep your real email address private, create a nondescript google/yahoo/hotmail account just for this purpose.
If your email address also contains a company URL they might be close enough to drop the lost smartphone off at the reception desk for you.
Adding an alternate phone number where you can be reached, or adding the old enticing phrase, Reward if Found, are additional options.
It is easy to change wallpapers on smartphones. Just google “[your smartphone manufacturer] change wallpaper” and the directions will pop up.
Creating a customized wallpaper is almost as easy. You can do it with any photoshop type app, or using a free on-line service.