The CSS background-image property is used to specify the URL to an image resource to use as an HTML element's background. In CSS3 this property receives an upgrade allowing you to place multiple background images into one element, see the related examples below for that.
url()
A reference to an image file on your website server using a relative path, or full path domain referencing.
Video Tutorial: CSS3 Multiple Background Images For HTML Elements Tutorial
Create whole page backgrounds for your web documents
