Is Finder open? It’s responsible for displaying your desktop icons and files. If there isn’t a dot beneath the Finder icon on your Dock, click on Finder to open it. Otherwise, if your desktop files still aren’t showing up, try repairing your Mac’s system by reinstalling macOS. Boot Recovery Mode by restarting your Mac while holding Command-R. Release the keys when the Apple logo and a progress bar appear. When the Utilities menu appears, choose Reinstall macOS. (No data loss) Select Macintosh HD as the target volume and let the installer repair your Mac. Once it is done, you should be sent to the login window, and if all went well your files should be back.
Hope this helps!
I was using my Mac, I believe something popped up about a "library", then I noticed my screen saver was gone, ALL my desktop icons and files saved are gone, and the screen saver is the sierra mountain view picture.
