Not necessarily the whole bathroom is finished in wood. The material can be harmoniously combined with natural stone and ceramic tiles
The most appropriate option walls is the house, but because of its high cost, to use it can not all. To replace the frame, bathroom, wood can be finished with wooden panels and ceramic tiles in a contrasting shade or color of wood.
As flooring it is customary to use the same ceramic tile. There is a version of colors of tiles exactly resembling parquet, it is called "ceramic flooring". You can also use a planed Board, varnished, but this type of flooring has a short lifespan.
Original complement interior bathroom wooden bath tub, but its cost is prohibitively high.
To your attention photos of bathrooms under the tree:
As you can see, bathroom interior wood is quite exclusive, therefore, having the desire and money, you can repeat one of these design ideas in your apartment!