As long as it doesn't affect the outside, you can basically go as nuts as you want. Although technically luxurious/expensive stuff would demand the Floating Palace feat, but either way a battleship's basically a floating town and the exact power source/tech is left vague. It may be some cold metal plating and hanging cables with dark corridors and bits or rust, or sterile plastic brightly illuminated everywhere, or a cozier home style with wooden panels and assorted decorations.
Anyway I'll assume that everybody in the party who doesn't say otherwise boards the ship and hopefully advance the action by the weekend.