Background image problem in CSS

I am wanting to have a basic pattern background so something like this:

body {
  background-position:top left;

But what I am also wanting to do is have another background image that sits at the very bottom left of the page constantly when you scroll. I dont really know how to acheive this tho. I really want to use CSS to do it to and I know very very little about CSS. Could some one please explain to me how I could do it?
thanx alot:hugegrin: