Generally speaking, a photo slideshow in iPhone/iPad plays once and automatically stops after displaying its last photo. If you want it to repeat playing until you manually stop it on your device, go to turn on the Repeat function according to the following instruction.
Steps to turn on Repeat on iPhone/iPad:
Step 1: Open Settings on the Home screen, and tap Photos & Camera (or Photos) to continue.
Step 2: In the Slideshow settings, click the switch beside Repeat to turn it on.
In addition, you are able to set the time for each slide playing. You can set time to play each slide for 2 seconds, 3 seconds, 5 seconds, 10 seconds and 20 seconds. It is all up to you in following steps: Choose Play Each Slide for and scroll down to choose the time.
