Refreshing page with a new image

I currently have a stagnant image on my site:

body {
background-image: url("../images/1.jpg");
background-repeat: no-repeat;
background-attachment: fixed;
background-position: center;
background-color: black;

border-bottom: 8px solid  #7D8A28;

}

It's just that I want it to be a different image each time the page refreshes, so it auto changes to 2.jpg, 3.jpg, 10.jpg, whatever. (There are hundreds to choose from)

Could someone help me out with a solution? I'm not very good at this, and this is my first site.

Thanks.