body {

background-image: url("/path/to/image.png"); }
@media all and (-webkit-min-device-pixel-ratio: 1.5), all and (-o-min-device-pixel-ratio: 3/2), all and (min--moz-device-pixel-ratio: 1.5), all and (min-device-pixel-ratio: 1.5) {
  body {
    background-image: url("/path/to/image@2x.png");
    background-size: 200px 100px; } }

header {

background-image: url("/path/to/header.png"); }
@media all and (-webkit-min-device-pixel-ratio: 1.5), all and (-o-min-device-pixel-ratio: 3/2), all and (min--moz-device-pixel-ratio: 1.5), all and (min-device-pixel-ratio: 1.5) {
  header {
    background-image: url("/path/to/header@2x.png");
    background-size: 600px 50px; } }