I am using music books that I purchased on e-bay. It does require quite a few books, but it is also a very large area to cover. I am using liquid starch to apply it to the walls of the armoire. You can buy it at most grocery stores if you look for it.
I saw how to do it on Tracey's blog http://acottageindustry.typepad.com/. She did a mini tutorial about it. I used a small plastic bucket into which I put a small amount of starch. Use enough that you can dip the music pages in and wet them completely. I did find, however, that too much starch makes the paper very soggy and it tears even more easily. You need to squeegee out the excessive starch before placing it on the wall. Use your hand to do this.
I found it easier to smooth the paper out with my wallpapering brush . It does wrinkle fairly easily but can be smoothed out GENTLY. Otherwise it tears if you are too rough. I also wore rubber gloves as it is very sticky, more than with wallpaper paste.
I bought some paper napkins at Home Goods and cut out the butterflies from the napkin to add randomly to the area. One thing I like to do is cut off some of the margins of the paper with a paper cutter as I don't like the wide plain white margins. I have decoupaged some other things by tearing the pages and just applying it randomly instead of in sheets. It just depends on what you prefer. You'd be amazed at how stiff and smooth that it dries. I still have about half of the inside left to complete because of all the little shelving areas it has. So I'll share again when I'm done. If you need visuals of it go to Tracey's blog and look for the tutorial, it helped me a lot.