DIY: Gallery Wall Arrangement Ideas - plus many other guides, such as yardage guides for upholstered furniture, window treatment & terminology guides, area rug size guides, etc. This is an excellent resource!!!
How to arrange and display picture frames / photos (layout) ----- e.g. over ledge / floating shelf, over stairs/staircase, gallery wall --- How-To GUIDE on this site: http://www.sasinteriors.net/2012/07/useful-ideas-and-layouts-to-create-a-photo-gallery-wall/