Also, do not forget about the replacement of old and rusty pipes with new. Now many are installing plastic pipes. They really have excellent operational properties. It is worth noting that such pipes can last a long time without losing their properties.
As for the finishing of surfaces in the bathroom, the main requirement for materials is moisture resistance to materials. Good material for wall decoration, and sometimes ceilings is ceramic tiles.
Do not save on the bathroom, it plays an important role in human life.