I personally love this arrangement by Martha Stewart: http://www.marthastewart.com/272930/picture-an-easier-way

Keep the frames the same color or if using matting, a nice impact is to use the same size matting on all pictures. Then frame the picture within the matting opening. It makes for a cohesive look. Love the Martha Stewart way of haning pictures!

Also, before you start banging holes in the wall (like me) lay out enough butcher's paper on the floor, and practice with your framed photos. When you have an arrangement you're happy with, mark the butcher's paper and hang it on the wall. Drill your holes thru the butcher's paper.