>>23418980
A gym or two would make a lot of sense, they'd need one while in space anyway and I'd imagine it's probably easier to work most kit under pseudo-gravity than just free floating.
Maybe some amenities for visitors. If there's any chance of the ship carrying civilians or ground-pounders, they might not be as experienced with movement in microgravity. Maybe an officers' mess, and a conventional one if there's room. Food is important for morale and even if it's only a sometimes treat, being able to serve a meal that you can eat normally would probably be a capacity you'd want.
I suppose a big factor is if atmospheric or space is intended to be the primary mode of operation, since that'd determine if you want to have something like a big medical bay that's only properly accessible in space.