They were random people/the 'occupants' of the crypt, but he does have dealings/nightmares about his own brother (Ben)'s death and subsequent haunting as well!

The war he was in was the Vietnam war, so jungle terrain, Saigon cityscape, etc have all been seen.

Uhhhh he might also have a reoccuring nightmare about the hotel room he was tortured in for nearly 24 hours, his torturers, and the 24 ghosts that haunt them.