For this tutorial I'll recreate the poster on a smaller canvas. Create a new photoshop document of 600px by 848px. To start off with the background get an interesting texture from cgtextures, I got mine here (Image 3). Import it and resize it.
In my case, after resizing, it did not cover all of the canvas. To make the texture cover a larger area, duplicate the layer (Right-click the layer and select Duplicate Layer...) and place it on top. To make those two layers blend into each other, use a soft brush and erase the bottom of the top layer.
To darken the texture, we first desaturate it. This can be done with a Hue/Saturation adjustment layer (Layer > New Adjustment Layer > Hue/Saturation...). Set Saturation at -100 so the texture turns gray. Create a Brightness/Contrast adjustment layer (Layer > New Adjustment Layer > Brightness/Contrast...). Set Brightness at -111 and Contrast at +36.