Line them up. For a fool proof way to have your photo wall looking picture perfect, line up all the bottoms or the tops of the picture frames (whichever you prefer).  If you are looking to hang a large number of photo’s, create two rows with the top picutres lining up along the bottom and the bottom pictures lining up at the top.  This essentially creates a straight line down your wall. Here is a photo that explains this much better than I ever could!

Perfect Picture Hanging

Mark a horizontal line and hang picture frames or your childrens' art work on either side of the line.perfect for a back hallway

Picture Wall

I love the idea of a family photo wall. My Mema Katie had an entire wall in her house covered with at least four generations of family pictures.