Something that was always mentioned was how much space was on your ship. A room? Two? I personally think of below-deck space to be two large rooms, both to be explained later. I wouldn't change the number of rooms by the type of ship, but the space of them. Say, a skiff could have a small room, no bigger than half of a bunkhouse. A frigate could have a bigger size room, and a galleon would have enough space for a completely furnished cellar-size room, no matter the ship origin. The only exception for this would be the SI raft, for it has no space for a room.
Quality and Design
The quality of ships vary by the type, origin, and physical properties. The tavern room would change depending on color choice and origin, as well as chosen companions. The cannon room would change depending on your ship's "health", most likely varying by the fourth of health. I'd imagine the design in the tavern room to be classic table-with-chairs-and-companions, as well as a Yum tap and pictures on the walls. Also mentioned on the thread was the idea of pictures from your personal journey.
Grouping Opportunities (just for fun!)
The Pirates: Five People - Navigator, two on deck, two firing cannons
The Photographers: Three or more people - Navigator, one on deck, one in the cannon room
The Captain Suffering from a Glitch - Two people minimum - Navigator, one on deck.
Navigator - Pulled into battle if a slash is initiated
On Deck - Pulled into battle if a slash is initiated
Below Decks - Prompted to join battle every thirty seconds or so until rezoned or in battle
EXP is awarded to all those who a) fought b) fired c) cleared tokens
While this is just an idea, I have a sneaking suspicion that there is more on our ships to come. What do you think, pirates?