its a three hundred year old building i believe, one assumes that there must be designated decorators, decor designers that are used time and again. Watching the West Wing, yes i know its a drama but bear with me, the Oval Office was given a makeover to suit the incoming President, and a budget was set for each office, as one might expect it was an expensive makeover, but no one said they should ask the President to put his hand in his pocket. I suspect that no one would ask the question who pays for it, not like here.
I could be wrong of course.