Photos can be almost any size, and are predominantly a true to life representation of your product or a window into how you serve your clients. They can be simple factual descriptions or they can elicit emotion with dramatic lighting or unique perspectives. Photos can be a supporting element of a graphic or the entire document.
Choosing to print in color versus black and white is up to you and what message you are trying to convey. Color attracts the eye, and can have a lot of impact. Black and white photos can also work when used correctly. Depending on the mood you are setting for your display, choosing to stick with color or ditch it can make a big difference for your exhibit or trade show booth.