Craftsman-style bathroom needs serious improvement

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Q: I own a 1920s, two-bedroom, one-bath house in a modest neighborhood of Oakland, Calif. I am trying to decide how much of a bathroom upgrade to do, partly to make it more desirable for everyday use but mostly to improve it for resale. The bathroom is tiny, about 4 feet by 7 feet. I have put in a pedestal sink. The bathtub is in good shape, but it's mint green. The floor is marble and in good shape, but it's an ugly orange color that clashes with the green tub. Also, the tile around the tub needs to be replaced. There is no space for a towel rack aside from the back of the door, so I thought about putting in sliding doors on the tub to make the bathroom seem larger and to add another towel rack. It currently has a curtain. In order to do this, a wall would have to be built at the end of the tub to support the doors. My questions are: What should I do about the marble? Is it smart to keep since it's in good shape, or would it be better to rip it up and put down ceramic tile? Also,...