No rugs. It is busy enough. Use a bath mat when bathing/showering

I agree. Find a bathmat in a beige/brown color that blends with the floors. I would use the smallest size that would work for the function (warm feet at vanity or wet feet at shower).

For safety reasons I would definitely put a bath mat in front of your tub and in front of the entrance to your shower. Without them that could be a slip hazard. Other than that, I would not go with a runner. If you don't want the feeling of a cold floor underneath your feet, I would also put bath mats in front of each individual sink and one in front of your toilet. I wouldn't get something that has a pattern because your floor has enough personality as is. I would go with something simple, like something beige. As for the shape, a simple rectangle will do, it matches the geometric lines that are all around your bathroom. Then again, maybe you don't mind the cold floor, and in that case you don't have to buy more than two mats.