These obviously aren't game pictures, I just googled them off the net.  This list tells you where to find each item and how to use it.

Room Key 215: Kyle's room key.  You get it from Dunning at the front desk the first time you talk to him.

Copy of Room Key 215:  You find it among Jeff's things.  Make sure you put it in your suitcase.

Room Key 217: Louis swipes it for you.  Another key you don't want Dunning to find you with.

A regular #2 pencil that starts in Kyle's suitcase.   Use it to wind up Iris' mystery cassette tape.

A crowbar from the tool box in the linen room.  You use it to prop open the set of drawers in Dunning's office.  Put it back as soon as you're done with it, as you'll be in trouble if Dunning catches you with it around chapter 4.

A screwdriver from the tool box in the linen room.  It doesn't seem to have any purpose in the game.

One of the items Kyle was hired to retrieve, found in the linen room.

A fountain pen with an engraving on it.  

Liquor found down in the wine cellar.  You have to pick up the booze from the shelves and put it into the empty box at the center of the room.

Black light, located in a locker in the storage room (where you set up the Christmas Tree).  You don't have to get it, but it can be used to discover the code number on the seemingly blank piece of paper in the sealed basement room.

Iris' missing mystery tape.  Find it in the trash can in the laundry room.  You need the pencil to wind it up and the cassette player in Louis' room to play it.

A small red box, the second item Kyle was hired to find.  It's in a locked drawer in Dunning's office.  You won't get to open it until the end of the game, though.