This building represents the place in which Nick visits his doctor, in order to resolve his issues pertaining to himself and Jay Gatsby.
The Death of Jay Gatsby
This "light" represents Gatsby's desire to be with Daisy. Since, the light is on the Bucchanan property, this is why it could be seen throughout the novel that Gatsby was standing at the end of his dock at night reaching out for the light, or more figuratively speaking, reaching out for Daisy.
The Valley of Ashes
These eyes represent the "eyes of God". Also these eyes on the billboard show how the government is watching over everything.
Tom's Investigation of Gatsby
The swimming pool represents the scene in which George Wilson comes to Gatsby's mansion and shoots Gatsby in the back with his gun. George Wilson acted in this manner due to the thought of Gatsby killing his wife with his yellow custom car.
This billboard represents the area between Long Island and the city during the late 1920's and early 1930's. In deeper thought, the billboard is also a key representation of the cruel conditions pertaining to the working class of the 1930's.
This room represents the scene where Tom Bucchanan finally figures out the truth about Gatsby.