Another addition to the new living room

I finally decided on a way to display some of my underwater photography. ShutterFly let's you configure a series of photos as a wall display.

The photos (12x12) arrived last week. The wall template has not arrived yet and I wanted them closer than in the template anyway so I decide I would hang them on my own. How difficult could it be to hang 6 12x12 photos in two rows of three so that they are perfectly aligned??

REALLY DIFFICULT!!