I find the way an image can be affected when placed along side another interesting. The resulting image takes on a narrative quality and the visual processing alters significantly. I've experimented with this a little in the past, usually when physical prints are lying around to play with.
More recently I've been using 5x4" work prints from 'Into Reverie' and 'Ghosts in the Wall'. When looking through the work I started to notice interesting juxtapositions where the colour, composition and subject matter would be complimented and enhanced by a particular union.