If you are going to store things in the blog it could be call the container
If it is a place for special item then it can only be called the pool room
you could also consider the carport which is a shed without walls
hall is a meeting place but probably doesn't tie to sandman theme
work bench may fit the bill
back of the van is where things happen
through the arch is the way into the back of the van
van room or sandman room would be a shed a shed for vans
to take the above one more step and you's al liked shed what about sandman shed

any way these a couple of suggestions