For the fifth white cube (it's actually black): You have to drag your mouse over all of the pictures to reveal the symbol the pictures has hidden. For example the hand, if you drag your mouse over the wrist, it'll reveal a symbol and if you click the hand, it'll reveal the number 2. Take note of the 4 symbols and numbers. Go back to the guy who shot himself and go to the locked box. Input the numbers for each symbol and get the black cube so you can put it in the fifth picture frame.
Please improve the server. I don't know if the server is bad but people are getting 200+ ping, sometimes 400+. Only 1 or 2 people in the room have decent ping.