Thank you so much for the map you provided for the Winter Palace, Greg King! It was invaluable on my recent trip.
Since the orientation of your map doesn't match the map that the Hermitage provides, I reoriented it to match the Hermitage's layout. I also went ahead and updated your key to match the Hermitage's key. (Thank you!)
First image: King's map reoriented
Second Image: Portion of the Hermitage's map that complements King's.
A. Malachite Hall 
B. Empire Drawing Room 
C. Silver Drawing Room 
D. Alexandra's Drawing Room 
E. Nicholas and Alexandra's bedroom 
F. Alexandra's Dressing Room 
G. Alexandra's Boudoir 
H. Nicholas's Study [180-81]
I. Nicholas's Bathroom
J. White Dining Room 
K. Blackamoor Hall or Arabian Drawing Room 
L. Nicholas's Gothic Library 
M. Rotunda 
N. Private Chapel [Closed. Can't Access. I repositioned the stairs on the Hermitage map and "created" a new room to show where it can be located!]
O. Nicholas's Billiards Room 
P. Nicholas's Reception Room [175-76?]
Note: Rooms O-P have changed. Whereas King's map has 2 rooms, there are now 3 rooms occupying this same space. If I can remember correctly, O  is quite small and P [175-76] is quite large. I think I IDed them correctly, but I'm not 100% positive. Perhaps a future traveler can confirm this point.