A great starting place to bring together multiple photographs is to utilize a grid. This could be a simple arrangement of photographs of the same orientation and aspect ratio in a two by two, three by three, or any number of photos by any other number of photos. Or you can take the layout further, arranging the photographs on an unseen grid that holds together the layout but can utilize photographs of different aspect ratios (1:1, 3:2, 4:5, etc.) and orientations (vertical or horizontal). There is a considerable amount of freedom allowed by utilizing a grid, but the constraints that do exist really help create a cohesive layout. This underlying grid can also help integrate text within the layout alongside the photographs.
Putting a photograph within a shape is a great way to go beyond the grid. The shape may be as simple as a circle or a complex repeating geometric pattern. Shapes are a great way to utilize a logo or graphic element that goes with a your branding. The arrangement of these shapes, holding photographs, can take on a structured grid like form or carefully composed freeform composition integrated with text and other graphic elements. There is a wide array of creative possibilities when it comes to using shapes, probably too many. There should be intension behind your decision to go with this approach, especially if it can be seen and understood.
Ditching the grid and confining shape approaches all together leads you down the path to a place where all rules and structure can seem to be thrown aside. At the end of that path you can see a nearly infinite array of possibilities when you take on a collaged approach to utilizing multiple photographs. You can take a cut and paste approach, as rough or refined as is appropriate. You can simply overlap multiple images in a manner that gets across the ideas you want to express with the combined photographs. With this approach, you can bring together various elements of varying size, color, texture, and perspectives in unique ways that can help tell the narrative of your photographs.