This is my approximation of the cabin on HMS Erebus of Commander James Fitzjames. It's mostly based on the picture below which was published in the May 24, 1845 issue of the Illustrated London News.
I've flipped the ILN picture from the way it was printed to make it accord with the ship's plans. The most noticeable feature on my view compared with the ILN's is the wash stand which the 1839 plans show to the left of the doorway as you go in. The space is no bigger than a decent size closet - about half the size of the en-suite bathroom of the hotel room I stayed in last week.