how to set div background image

1#avatar {
2    /* This image is 687 wide by 1024 tall, similar to your aspect ratio */
3    background-image: url('http://i.stack.imgur.com/Dj7eP.jpg');
4    
5    /* make a square container */
6    width: 150px;
7    height: 150px;
8
9    /* fill the container, preserving aspect ratio, and cropping to fit */
10    background-size: cover;
11
12    /* center the image vertically and horizontally */
13    background-position: top center;
14
15    /* round the edges to a circle with border radius 1/2 container size */
16    border-radius: 50%;
17}

1body {
2 background-image: url("paper.gif");
3 background-color: #cccccc;
4}

1background-image: url("photographer.jpg");

1background-image: url('./image.jpg');