Change post (not page) background to an image

Hey,

I’ve seen a few people mention this but I’ve not come across an answer that seems to work. I’m simply keen on changing the post background (a white rectangle) to some kind of recurring image, like maybe an actual page of paper or something – just to give it more character.

Any help would be great appreciated. Have added what I thought was the right code to the style sheet but nothing’s changing.