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.
It can be fun to change up the faucet design you will have in place for your bathroom though. You can transform it into something elegant if you want to give it an upscale feel without a huge expense. It is a good idea to look at images so you can see the various options available.
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.