background-x2image.styl

background-x2image($image) {
  $ext = extname($image);
  $image2x = pathjoin(dirname($image), basename($image, $ext) + '@2x' + $ext);

  background-image: url($public-image-path + $image);

  @media $retina {
    background-image: url($public-image-path + $image2x);
  }
}

main.styl

@import 'variables'
@import 'background-x2image.styl'

#logo {
  background-size: contain;
  background-x2image: 'logo.png';
}

variables.styl

$retina = 'all and (-webkit-min-device-pixel-ratio: 1.5)';

$relative-image-path = '../assets/img/';
$public-image-path = '../img/';