Sand Photo Envelope Effect
You can create this effect with your own photos.
Click on layer settings. Then right click one of the photo slides.
Click on your photo. Click on the other photo in the layer list
And select the same photo
OK. Now you have changed both photos in the one slide.
Click on the next empty slide and hit paste.
Now repeat the steps and change the photo again.
This shows the directions, how easy it is.