Good advice. As to why I didn’t simply create a bitmap of fractal noise, well, I had it in mind (assuming I could work out how) to use the fractal noise in some way to enhance the perception of depth. Right now, the paper layer is completely flat. It would be nice if I could subtly bump-map the layer, based perhaps on the fractal noise, and have this change be realized, visually, by the spotlight I have shining on it. It would be subtle but apparent, and would enhance the sense that the paper is scrolling by a fixed camera.
I’ll look into duplicating the layer I’ve got. With luck, it won’t be as cpu-intensive as having a layer of the needed width, and hopefully the repeat nature of the noise won’t be apparent.