Actually they're both
photos of the same mockup!
The Boeing and Planepictures.net photos both represent something close to the current design being shown to airlines, but the mockup is still missing some practical details (exit markings and cabin doors etc) which will detract slighly from the clean design currently shown.
Plus I can't see any
airline opting for the completely open design with no cabin dividers and curtains between classes!
It's also worth noting that some details shown on the mockup such as the arched entryway area are optional extras (at extra cost) and as such will not be standard on all 787s.