Directly connected to their quarters, the captain’s office on Potemkin was limited in space and use compared to later “ready room” designs; though when the Excelsior class was new, this space was a big improvement over the integrated offices for captains on Constitution-class ships.
There were two entrances to the room: The main door leads directly to the ship's corridors; while the secondary door next to the replicator leads to the captain's quarters. Thus the ship's CO can move freely between their living spaces and this work space when they're not needed on the bridge.
With Captain Bertrand being passionate about early Earth space travel, most decorations focus on that particular topic. The old Earth sword placed next to the desk, on the other hand, was a tribute to the time period of the ship's namesake. It was something of an unofficial tradition for captains of Potemkin to personally give the sword in hand to their replacements to signify the transfer of command.
(The Excelsior model used is by Chris Kuhn, with texture and material modifications by myself. The Apollo-Soyuz painting is by Davis Paul Meltzer for NASA, 1975. The Phoenix warp ship painting is by Mark McHaley for the book "Star Trek: Federation – The First 150 Years", 2012.)