Classic use of standard white paper.
Who gave the quote about once you've wallpapered your writing room with rejections, then and only then are you ready to publish?
I've googled the phrase and mostly end up with snippets about writings saying "if you're crazy enough to wallpaper with rejections ..." or "don't give up and don't you dare use it as wallpaper."
All n all, I think those people are taking the quote a little too literally. I believe it refers to the amount of rejection, not the application of the little paper slips. Although, I do tack them up to my bulletin board to remind me that I am a writer and that I am attempting to do something that will get me published. That, and I'm not some fragile flower that wilts at a quarter sheet of paper saying "sorry, but no."