Eh, if the question is "will they let you if you ask them" then the answer is obviously no and why would you ask. If the question is "can you stash your bag in a cubicle for a while without anyone caring" then the answer is almost certainly and who would care. Especially the cubicles in the back of the C club. If you're in the B club, I would leave it by where the workstations are (I think there's even a luggage rack there), but I'm not too risk averse about these things.

at JFK, I just stashed a bag in the luggage racks for a little while nbd (in the main concourse AC that is adjacent to the FL). Just be reasonable and don't be a terrorist.