body {

background-image: url('/path/to/image.png');

} @media (-webkit-min-device-pixel-ratio: 1.5), (min–moz-device-pixel-ratio: 1.5), (-o-min-device-pixel-ratio: 3/2), (min-resolution: 1.5dppx) {

body {
  background-image: url("/path/to/image@2x.png");
  background-size: 200px 100px;
}

} header {

background-image: url("/path/to/header.png");

} @media (-webkit-min-device-pixel-ratio: 1.5), (min–moz-device-pixel-ratio: 1.5), (-o-min-device-pixel-ratio: 3/2), (min-resolution: 1.5dppx) {

header {
  background-image: url("/path/to/header@2x.png");
  background-size: 600px 50px;
}

}