OK...... I GOT IT
1) In the first picture, the closeup of the skull, cards, and knives---- it is in Danny's picture from a different angle: on his desk.
2) In the picture of the bird, it is a closeup of the HAND in ADAM's picture, in the hand on Adam's desk with a bird on it.
3) Maynard's picture has nothing in it that is in any other picture.
4) In the picture of the grisly head with a tube hooked up to it and the oxygen tank in the background--- that is in Adam's picture--- look to the left of him behind him. Same stuff - the oxygen tank, the head and all the other stuff, just taken at a different angle.

I don't know what it exactly means, or what kind of puzzle it is, but maybe you guys can go from here........... Sorry if somebody had already brought this up.