Plug-in Menu Location: Python-Fu/Create New/Yearbook Page...
Have an image with an active layer opened (any image will do [not used]).
Run Plug-in (Python-Fu/Create New/Yearbook Page...). Choose color or black & white. Choose number of columns and rows of (images/photos of people). Click OK to run.
After it's done, you might want to scale down the result as it's generated in full resolution so it's quite large and you might want to add a caption for fun like (ie. "1990 Yearbook", "GL Employees 2018")