Sometimes you may want to force a background image or a color such as on a splash page or opening screen to be different than the rest of the site. The example below illustrates how to do this with a HTML snippet.  Remember it is imperative you have both <style> and </style> tags otherwise your entire page will have to be deleted and you have to start over.

<style>
body, body.template {  background-color: #000000; 
background-image: url('bg2.jpg');
background-position: center top;  background-repeat: repeat-x; }

</style>

Note:  To add a large background use a File area on a different page and a permalink in the URL above.   Otherwise for very small backgrounds you can use Site Properties and upload a file directly as long as it is less than 20k in size.