Now for this image we want to create a really textured background, faintly resembling paper. So the first thing we need is ... a paper texture!
Happily you can grab some really awesome grungy paper textures from Bittbox and they are nice and large too, which is good because this is a huge canvas.
So I can't remember which texture I used first, but grab one, desaturate it (Ctrl+Shift+U) and stretch it over the top to fit the canvas.