We love this impromptu-looking curtain tie made of a strip of leather. Ribbon would be swell as well. (The trick is to find one with enough texture so it doesn’t slip).
It reminds us of our improvised hotel room strategy for calming down drapes with busy prints: We fan the drape out and pull the neutral lining toward the room. Then, we twist the whole curtain so that it becomes a neutral column and wedge it in the corner OR use the inevitable shade cord in the corner to wrap it tight.