First up, a polaroid collage. A riff on his famous pool paintings of the late 60's, early 70's.
There's a number of well-known Hockney photo-collages, and they tend to give the impression that they're easy to do. They're not. Just google 'Hockney photo-collage' and you'll find a number of works inspired by Hockney, few of which are remotely interesting or compelling.