To have more choices to use as a shower curtain (and therefore, more choices for wall color), I suggest using a clear plastic inner curtain (at the standard height, on the rod that was probably already there) and buy a spring rod (comes in different colors, about $17; found in the bathroom section or where other rods are located; I bought mine at Walmart where they are located in the bath section).

Go look at king-sized sheets. Find one you like. If needed, cut vertical slits (on the inside of the sheet, on the inside of where the fabric has been turned and stitched down) in the top 2" hem of the sheet and insert the new rod if needed (some sheets are already open on the sides). Cut only as much as needed to slip around the big rubber end of the rod. Position the rod up against the ceiling.

The length should be perfect, assuming standard wall height. You'll be warmer in the shower, too.

Then take color inspiration from the sheet for walls and any rug in the room. The gray floor looks great and is a good neutral, so it should go with any shower curtain treatment.

I have used this sheet idea as an outer shower curtain for many, many years. Since it goes all the way up to the ceiling, it makes the room feel taller and adds star power to the room.