It takes a bit more effort, but silhouetting (removing the background) and overlapping mug shots can add life and fun to even the driest of subjects. You can create some lively, interesting layouts with this technique.
When using photos of varying sizes you could raise unintended questions about your editorial slant. Is the larger photograph perceived as the most important person? Might someone feel that you or the organization is slighting them by using a smaller photograph or by placing it behind someone else? These are simply points to consider when choosing a mixed layout.
