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SVG-background-images-PNG-retina-fallback.css

body {
  background-image: url(../img/pattern.svg);
}
.no-svg body {
  background-image: url(../img/pattern.png);
}
@media only screen and (-moz-min-device-pixel-ratio: 1.5), only screen and (-o-min-device-pixel-ratio: 3 / 2), only screen and (-webkit-min-device-pixel-ratio: 1.5), only screen and (min-device-pixel-ratio: 1.5) {
  .no-svg body {
    background-image: url(../img/pattern@2x.png);
  }
}

SVG-background-images-PNG-retina-fallback.scss

// ----
// Sass (v3.3.0.rc.2)
// Compass (v1.0.0.alpha.17)
// ----

/*
 * http://zerosixthree.se/8-sass-mixins-you-must-have-in-your-toolbox/
This mixin depends on Modernizr and creates a bit more work for you when creating images for your site, but it’s really worth it in the end.
You need one .svg file, that will serve as the default background image. You’ll also need a regular .png that serves as a fallback for non-svg-supporting browsers. And last you need a twice as large .png as a second fallback to retina screens.
All in all you need this:

* pattern.svg
* pattern.png
* pattern@2x.png
*/
$image-path: '../img' !default;
$fallback-extension: 'png' !default;
$retina-suffix: '@2x';

@mixin background-image($name, $size:false){
    background-image: url(#{$image-path}/#{$name}.svg);
    @if($size){
        background-size: $size;
    }
    .no-svg &{
        background-image: url(#{$image-path}/#{$name}.#{$fallback-extension});

        @media only screen and (-moz-min-device-pixel-ratio: 1.5), only screen and (-o-min-device-pixel-ratio: 3/2), only screen and (-webkit-min-device-pixel-ratio: 1.5), only screen and (min-device-pixel-ratio: 1.5) {
          background-image: url(#{$image-path}/#{$name}#{$retina-suffix}.#{$fallback-extension});
        }
    }
}

// example of usage
body {
  @include background-image('pattern');
}