Snapshots of vacation, graduations, or fine art prints probably play an important part in your home decor. But not all photos are "art" and each category needs to be treated in its own way.
Fine art photographs, in black and white or color, should be treated like other pieces of hanging art. Photos usually lend a casual feeling to the room so I use them in less formal areas of the house. In groupings it's best to keep black and white photos separate from color unless the images are linked in theme. Framing and matting should be simple and complement the room's decor.
Black and white formal or professional photo portraits can be gathered into a family gallery. Mounted in large white mats and simple black frames, a collection of photos becomes a dramatic focal point in a family room, hallway, or study.
Smaller casual snapshots I treat like accessories. I group them in similar or matching frames and arrange on shelves or tabletops (if you can't see the back of the frame.)