It’s annoying for your Mac to decide, “Hey, we’re not actually going to use this picture anymore,” and revert your wallpaper back to a system default automatically. Fortunately, there’s an easy way to ...

You should log out of iCloud on your Mac if you plan on getting it serviced or letting someone else borrow it.

You can turn on AirPlay to use on your Mac computer through the System Preferences app's "Displays" menu.