Pottery Barn has a great tool for decorating tips. I found some tips for wall displays. Find them all here: How To Create a Memory Wall, Three Tiered Display and Gallery Display.
Three Tiered Display: A simple three-tiered display is ideal for small spaces such as the bathroom or study area. Begin by choosing two long rectangular frames to hold 3-5 small portraits or photos. Hang these two frames horizontally on top of one another about 12-16 inches apart, depending on the size of your space. Hang 3-4 medium frames between the top and bottom rectangular frames. This will create a tight square-shaped display, perfect for small spaces.
(Please note this is a stock product page. This image is not my photography.)