Here are the options I am considering:
Eames Walnut Stool
Pros: rich and warm wood color; easy on marble floor.
Cons: pricey. Wood and moisture don't go well.
West Elm Martini Side Table
Pros: great-looking, functional and affordable.
Cons: aluminum is hard on the floor unless the entire bottom is covered by felt.
Tolan Lucite/Crystal Stool
Pros: sparkly, works well in a bathroom.
Cons: might disappear into the background.
Pros: a popular choice in a bathroom. Easy to clean and low maintenance.