Our box room is a little over 6ft square, and not really much use as it's so small. At the moment, toddler DS is crammed in there until BIL moves out, and then he will have a bigger bedroom. So when DS has vacated this tiny space, what do we do with it? We have a 5 bed house and we already turned one of them into a dressing room (DH's job means he often comes and goes in the middle of the night, especially in winter. The dressing room means he doesn't disturb me when he's getting ready for work or bed). We have easy access to the loft so don't really need it as storage, we've no need for an office/study either.
Before DS came along, it used to be a toy room for DD but just playing with one thing completely filled the floor space and you couldn't move in there. DH wants to turn it back into a toy room for both kids but it was ridiculous with the toys for one child, never mind two!
So inspire me, what do you do with your tiny box room?