Jan, I have done a lot of large scale projects in the past, even covering an entire set for an opera with sheets of paper that I had marbled myself. It survived a tour of performances around Britain & was still looking good 8 years later after (having been stored in a barn). I have also done a bathroom & a wall plus a floor, in my first house in London. It works very well but you have to use the right glues/pastes for the job & a good sealer afterwards. On a floor you obviously have to seal it several times. I have also done several pieces of furniture in the past, the most successful was an ugly, but useful, bureau desk made in the wartime austerity style.  

It is easy & fun to do.  I hope you have as much fun as I did. I used a lot of PVA both for the initial glue & as a varnish. Try a sample board first to practice on before you start on the walls. 

Have fun & let us see a photo of the result.   

I seem to remember having to paint the wall with PVA because it sucks the glue from the paper. I think a small craft roller is useful for smoothing out the images on the wall if there are any bubbles (pricking the bubbles with a needle also helps).

I must find the bits of my decorative fire-place screen I made & decoupaged with flowers in a three-dimensional papier mache vase. I used some of those sheets of wrapping paper with full page reproductions of Dutch seventeenth century paintings of vases of flowers in a still life.  I will try to re-assemble it & post a photo. 

Great news, Jan, glad you are enjoying yourself.    I have just remembered that I used to work on a board I covered with that non-stick stuff you line your oven with (Lakeland used to sell it but now I think you can get it in every £1-shop).  It is a trick I learnt when making my theatre models. It makes it easier to wipe any glue-y messes clean.  

We bought those liners at Poundland last week. They are very good.