Well, Close to my Heart's Flip Flaps are the answer! These are 4 x 6 pockets that you can slide your photos in. They have an adhesive side and you can layer as many on top of each other as you want.
On this layout I stuck 3 of them together, put my photos together and then adhered the flip flaps to my page protector...on the outside. Now I can "flip" through the pictures on these layouts without having to create additional layouts! I LOVE these! They come in a package of 15 for just $3.95. I find I use a lot of these on those vacation pictures. Give them a try!