Loading library photo images into screen saver.
In the Apple System Preferences Screen Saver Settings, I choose Photo Library -> Photos as the Source for the slideshow images to be used when the screen saver is activated after 20 minutes of inactivity. When previewing the Screen Saver or the actual screen saver is activated after 20 minutes of inactivity, a black screen appears on the computer screen. No photo images are displayed by the screen saver.
MacBook Pro 15″, OS X 10.11