Hi Janie,
Much will depend on how much of the original image from the wallpaper or wrapping paper is visible in the final collage. I assume quite a lot, otherwise you would just use plain paper. If that is so, then there is a good chance that what you want to do, if sold commercially, would amount to infringement. Whether the manufacturers of the wall or wrapping papers would be bothered about taking action against you is, of course, an entirely separate matter.
Infringement occurs when a
substantial part of the original is copied without permission. Assuming that both the wall and wrapping papers have relatively simple designs it would not require much of the pattern to amount to 'substantial'. Copyright law takes no account of the artistic merit inherent in a work, so even a fairly basic juxtaposition of colours and or basic shapes, is likely to be protected. The actual act of copying occurs when you photocopy the original. If instead you just used the original paper as the background, you would be on much firmer ground since nothing would be 'copied', merely re-purposed, which is generally speaking OK. There is some slight risk that the moral rights of the original artist could be infringed by overpainting etc, but I think that that would be very hard to argue, given the utilitarian and largely ephemeral nature of the types of artistic work we are considering. Nobody could claim derogatory treatment of their work just because a piece of old wrapping paper was used to line the budgie's cage. And of course, as long as you were doing this for your own personal use, there would be no problem. The use of copies for the purpose of instruction would technically infringe, but assuming this was face-to-face instruction, as opposed to a Youtube video, you are unlikely to face a claim over that particular aspect of what you want to do.
As far as the use of patterned fabric is concerned, this is entirely OK. Fabric is sold to be made up into other items, be it garments, curtains or perhaps, brooches. There is no copying involved and thus the so-called
exhaustion of rights doctrine applies here, as it would if you used the wallpaper itself and not a photocopy, for your collages.