Joss Whedon stated, of the ship, “There are not fourteen hundred decks and a holodeck and an all-you-can-eat buffet in the back. It's very utilitarian."
The Serenity feels almost like a college dorm, with cluttered spaces and a mess hall with picnic tables. The rooms are even color-coded to match the characters that hang out in them.
As an example, Whedon stated that “the engine room was rusty brown because that's very earthy and likable and real, and that's Kaylee's space — that was very deliberate.”