Note the large 3-part window in the wall on the right (the east wall) of the East Room in the c. 1920 photo. This is actually a doorway to the terrace that forms the roof of the east collonade of the White House. Note how deeply set into the wall this doorway is. Actually, the interior wall of the room is a false wall. Behind it is the original wall of the structure, and in that wall are two windows on either side of the doorway. When one views the external wall from outside, one sees that the windows seem to be whited out.
I wonder why the East Room could not be restored to its original design, thereby admitting more daylight into the room. It seems that the two fireplaces that now occupy this wall could be redesigned and placed between the two windows found on either side of the terrace doorway.
By the way, a window in the State Dining Room has also been covered by an interior false wall that also covers a portion of the doorway leading to the terrace over the east collonade. Only one window can be seen to the south of this doorway when an exterior view clearly displays two windows.

James Goode's Capital Losses contains an image of the library at the Soldiers' Home with similarly-wrapped chandeliers. According to him, this was done to protect against flyspecks - apparently a problem in pre-AC D.C.

lots of pics of the renovations including a photo of a bulldozer (per tracy) are at this link

http://www.trumanlibrary.org/abierowe/whitehse.htm

The White House was completely gutted during the Truman administration and the interior was created anew with a steel frame interior support. The plasterwork in the East Room was not salvageable and it is different today.

I remember reading a chief usher's memoir of working in the White House in the '70s ("Upstairs at the White House"). The reconstruction was triggered when Truman noticed a chandelier swaying as a result of an usher walking in the rooms overhead. Truman had to live at Blair House for a couple of years during the renovation. It really was totally gutted-- there are photos of bulldozers inside the shell of the building.

This is a great shot... Made me think of the movie Cocoon right away... or the pods from Invasion of the Body Snatchers! Pretty eerie.

Where is Christo when you need him? They only got part of the room done.

Are those chandeliers wrapped in cloth to keep dust out?

According to the White House web site, this room is traditionally used for dances and parties -- clearly not at the moment this was taken, though. The piano was replaced in 1938, but the benches are still there.