We store bikes and other unsightly things under stairs.
How would you go about putting a curtain with a drawstring in front?
Here's someone who did something similar: diydiva.net/2010/03/how-to-easy-fabric-curtains but the curtain there is not easily drawn.
For our home, we simply used a draping thread-curtain. The curtain is made of individual strings which we hang on the staircase itself. The strings will drape down and we cut the remaining threads according to the height that we require. Previously the storage underneath there was open and look a bit unsightly too. But with the "door" guests will not be too surprised like previously they had before.
A photo of the space would help.
If it's triangular/trapazoidal, as in the photo you referenced, and you want a cord-operated mechanism, the only solution I can think of would involve drawing the curtains toward the top, since otherwise they run into the floor ... unless you can come up with some really weird mechanism to bundle the curtain as it moves. Of course the whole thing doesn't have to move, just the portion you need easy access to.
Alternative solution: Rather than moving the curtain to the side, roll/gather it upward and tie it in place, as was done with the sides of old tents. Simple and effective.
