Loop the slideshow and the main audio track
You can set the slideshow to loop (play repeatedly) in full-screen mode until you stop playback by pressing Esc. You can also set playback of the audio clip in the slideshow’s main audio track to loop until the end of the slideshow.
Loop the slideshow or the main audio track
Select a slideshow album in the Library inspector.
Click the Slideshow Settings button in the lower-right corner of the Slideshow Editor, and click the Default Settings button.
In the Default Settings pane, do either or both of the following:
To set the slideshow to loop in full-screen mode until stopped: Select the “Repeat slideshow” checkbox.
To loop playback of the slideshow’s main audio track: Select the “Loop main audio track” checkbox.