We use the same closet organizers that have already been posted. A small box on each shelf turns it into a very easy dresser.
Is there a way to access the space under your co-sleeper? Could you organize the baby clothes into small boxes (one for short sleeves, one for pants, etc) and place those boxes into a large box or wooden crate that you could slide under the co-sleeper? Then you'd be using only the space you already have set aside for baby furniture.
Could you mount a shelf in the corner over the co-sleeper? Like a stuffed animal net. Then you could use those
pop-out canvas drawers
and everything would still look nice.