The aged box and photographs are sublimely aged, like something that's been discovered in the mustiest corner of the attic. They look, feel and smell perfectly authentic, and their musty, clammy texture means you won't fall into the trap of treating them like playing cards. There's no way you'll be shuffling these! They need to be handled like old photographs.
There is a wealth of opportunity for spinning an atmosphere, telling of the Victorian practice of posing and photographing the dead, the whole field of spirit photography, focusing in upon the story of Coleman as the seance proceeds. The method is simple and foolproof, allowing full attention to be given to building the atmosphere.
I would note that the effect takes a few minutes to manifest (not a problem as it allows you to tell the tale while the 'medium' focuses, it's easily incorporated into the pacing). It is also quite subtle, and all the eerier for it. This is an effect that relies upon a slow, creepy build-up of atmosphere and delivers a disquieting shudder and definite unease at its conclusion rather than the wham-bam finish of a 'trick'. It is very convincing and will leave your audience unsettled.