transparent-background-image.css

/**
 * A cool trick for making a transparent background image 
 * using only pseudo-elements.
 */
  
body:after {
  content: "",
  background: url(/path/to/your/sweet/image.png) no-repeat center center fixed;
  background-size: cover;
  opacity: 0.1;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  position: fixed;
  z-index: -1;
}