As I've been doing ship deckplans I noticed something about a great many starships of fiction. Where the hell do they keep the toilets? All right I got past that and I don't want to write a post about it anyway. For some reason they don't even call them bathrooms or lavatories they're 'freshers.
Another point often glossed over is where the heck do crewmen store their belongings? I loved the officers' staterooms in Star Trek's various eras (I can't call them cabins, the damn things were biggers than some places I lived) but there weren't any obvious closets. Did they just fabricate everything they needed? Did they have only what they needed in the few drawers I did see and store bigger items in the cargo deck?
It was also peculiar in Next Gen era Trek that the only recreations facilities we ever see are the lounge and the holodeck. Yes. The holodeck could be a basketball court or bowling alley, but it takes up a lot of power and computing time that might be better used. A few empty gym sized rooms and a replicator could set up whatever sports arena you wanted within reason.
But where do they keep the emergency gear? I went back to plans I had done and began sticking emergency lockers all over the place. Maybe they aren't all placed perfectly because hey people aren't perfect and you might have other things you need to get to more often than emergency gear but they are there.
I'll note some seating arrangements may have a storage compartment for gear as well. Canny crew will have made alterations to keep gear they might need nearby but this gear is often the type that involves stabbing and shooting people and realy there are a lot of other kinds of more likely emergencies.
I will just say whatever the technology of your setting, no matter how cheap hauling mass across the stars becomes hauling less mass will be cheaper still. Storage space is precious but necessary
1) First and foremost I think a locker would have a fire extinguisher. A fire aboard a vessel is very bad whether at sea or in orbit. Some vessels will have fire suppression systems but you can never have too much firefighting gear.
2) Breathing masks are another must have, something like the compressor/filter masks many settings use. A compressor feature will let you breathe and stay conscious longer in a compartment that has been breached. That may save your life. The filter part helps if there is smoke or other contaminants.
3) Hull patches and tape. These are crucial for stopping up that pesky hole letting the vacuum in. Hull patches and breathing masks are damage control gear. Spacesuits are for salvaging wrecks or doing maintenance. The theory is any weapon making a hole in a compartment big enough to suck you out into space would surely kill you outright. So far no one has stepped forward to dispute this.
4) Flashlights. All this good stuff is useless (except the breathing masks) if you can't see to use it.
5) Magnetic/micro-hook/grav soles or other foot wear that lets you stand in one place and work on things. This is particularly useful when ships have artificial gravity of some kind (whether centrifugal, constant boost, pet black hole or handwavium induced) and crew are not used to zero gravity work.
6) Tools. Tools are nice, one for prying, one for banging, a couple for screwing/twisting. Throw in a couple of rolls of tape.
7) Survival/Repair Manual(s) Have a bunch of these on a tablet with a very long duration battery.
8) Medical Kit something that holes your ship could leave you alive, barely. Fires and other accidents can also leave you injured but alive. Antiradiation drugs and painkillers are a must. A pressure drop could cause the bends and you might want to take the edge off that long enough to fix whatever caused it.
I'm sure I left something out. I'd like to hear from those with more experience on what to include in one of these lockers. If you bought Ships of the Galaxy: Hawking Courier you'll see I included DC lockers and they're pretty big. They could probably be smaller if I knew what goes inside better.