It looks pretty good but like you said there’s something missing, I think it’s the lighting that’s off. Perhaps consider adding more decor to the room and enhancing the overall level of detail. That’s all I can really say.
Otherwise, well done on your work.
The lighting and general emptiness of the room is the major issue. If you add more decor and maybe add things to the walls, it would look better. Placing things on display around and inside of the shop would help a lot too.
Dimming the lighting or at least making it look less flat would be another good idea. Try to use future lighting and point lights in specific spots to illuminate a room, rather than bright lighting everywhere.
Typically, in locker rooms there are walls of lockers throughout the room, organized into various patterns. Yours are just on the walls themselves, which creates an empty feeling.
This looks more like a fancy hall than a locker room. I walk into a locker room every day and expect rows of square lockers with benches in between, along with showers.