Since the 1930s, Airstream has been designing very small bedrooms for some of the tiniest homes on the market. Their trailers are a great place to look for ideas for closet-sized spaces (without wheels). Click below for a few small-space concepts.
The curtain leading to the bedroom in this DWR Airstream separates the area visually while taking up very little space. In a studio apartment, a curtain is a simple way to define the bedroom area and give it a little bit of privacy.
The windows surrounding the bed in this Classic Limited Model make the area seem much larger. Although it's not feasible to add windows to your apartment, an accent wall papered in an outdoor theme (like the Cavern Home Blackbird Wallpaper) could visually extend the space. Another idea would be to hang curtains on the walls surrounding the bed to create the illusion of windows.
This seating area from the International Ocean Breeze Model would work well as a sleeping space for guests in a small apartment. A daybed with storage underneath would follow the same concept.
Almost all of the Airstream models include cabinets above the bed for storage. If you don't have a closet or room for a dresser, it's one way to add space to put your clothes.
A wall-mounted sconce in this Safari Model provides reading light without a bedside table.
This is a good idea for guest rooms or childrens' rooms. Arrange two twin beds opposite one another. With bolster pillows along the wall, they become a pair of sofas. This photo is from the Basecamp Model.