The Edwardian and Victorian styles of the time are still a popular choice today. They look exquisite in a villa or cottage bathroom and never loose their appeal in terms of design.
The key to decoration is neutral tones with a few dark colors. For the walls choose a matte or flat wall paint. Pale golds and yellows work particularly well as does floral or check patterned wallpaper.
The ultimate luxury in a fantasy bathroom would have to be a waterproof TV. You could even think of doubling the bathroom up as gym complete with exercise bike and rowing machine. Ornaments should be unobtrusive so choose things like small piles of pebbles and modern wall prints over candles and nick-nacks.