I may be missing something here. How is this easier or better that simply painting a wall?

It sounds like what you want is a self-adhesive wallpaper. This might be nice because it avoids the mess, but a liquid paste has the advantage that you can slide the paper around while it's wet to adjust it. I've applied contact paper enough to know that it's really hard to get it straight because it won't slide around. Maybe it would be possible to create an adhesive that can be preapplied to the paper that is slippery temporarily before curing. I don't know if it's really feasible, but it would be great for this and for some other self-adhesive products like tape and stickers.

Ok, I reread your post and realized that I missunderstood your intention. You really want a transfer system that works like a fake tatoo or iron-on image. This might be hard to apply to a typical textured wall. I'm not sure that this would be as effective as regular wallpaper. The paper in the wallpaper provides considerable strength, which enables it to cover underlying rough textures.

Dwane, that would be right. A paint job that would work just like a fake tattoo, iron on image or even a sticker job that has the adhesive preapplied to it that allows curing time. I understand that it might cause a bit of trouble on a textured wall and one may have to smoothen it first. On a typically smooth wall that would be a non issue.

And Hyenuf, why ever invent a motorized toothbrush when a simple brush would do the job just fine!

I didn't realize I was credited with the invention of the motorized tooth brush.