You asked this yesterday and it was answered in this thread that you started:
http://www.subsim.com/radioroom/showthread.php?t=111304
That thread links to a mod that someone created earlier that shows what file and where it is located that you want to change.
The thread in question is Pacific Theater Map 1941-1945 at
http://www.subsim.com/radioroom/showthread.php?t=109549
This link explains how the modder changed the map on the desk in the control room.
Good luck.
EDIT: Humm.. On further reading it looks like you are not talking about the map but rather the desk. My bad. Appologies