What do you call a tiny room off a hallway or room for storing linens? In Canada, that is always a closet. A cupboard here is usually a cabinet mounted high on the wall or from the ceiling, though cupboard is also still used for the original piece of furniture for holding dishware, etc. I ask because I am curious about the words used for things in other places.
A tiny room off the hallway could be called a storage room but if it is used to store linen, it would usually be called a linen cupboard. We use cupboard for everything. Our clothes cupboards, kitchen cupboards, linen cupboards, bathroom cupboards, etc. A cupboard in Australia can be built-in or free standing (for example, it could be built-in within a wall recess or under stairs, built-in wall-to-wall, attached to the kitchen/bathroom walls or any size free-standing).