I don't think I would use black shower curtains to make a room look larger, but the idea is a good one. Maybe curtains the same color as the tile, or a loghter shade of taupe. Floor-to-ceiling shower curtains. Make a small bathroom feel more luxurious.
nice cool A soft, inviting, budget friendly bathroom remodel for less than $100
Bear Bathroom Door Shelf - A Black Forest Decor Exclusive - Give your bathroom storage a boost with the Bear Bathroom Door Shelf, featuring three over-the-door mesh baskets with black bear cut-outs on a wrought iron frame. Measures 12 x 5 x 35 ~