AFAIK, there is nothing that you can put under a regular paper that will stop it from absorbing the moisture in the room. You might be able to paint the wallpaper with a clear waterbased varnish but you risk activating the wallpaper paste.
Not all vinyl wallpapers look cheap. The following company sells vinyl paper at up to £370 per roll.
FAQs Why should I get some bathroom wallpaper? The bathroom can often be overlooked, but there's no reason to settle for a bland design - st
www.wallpaper-uk.com