.logo {
  background-url('logo.png');
}

@media (-webkit-min-device-pixel-ratio: 1.5),
       (min--moz-device-pixel-ratio: 1.5),
       (-o-min-device-pixel-ratio: 3/2),
       (min-device-pixel-ratio: 1.5),
       (min-resolution: 1.5dppx) {
  .logo {
    background-url('logo@2x.png');
    background-size: 200px 300px;
  }
}