Sass-mixin for SVG + PNG-fallback

svg.css

.lt-ie9 .error {
  background-image: url("images/sprites/sprite.png"); }

.error {
  background-image: url("images/sprites/sprite.svg"); }

svg.scss

@mixin img($name, $dir) {
  .lt-ie9 %img_#{$name} {
    background-image: url("#{$dir}/#{$name}.png")
  }

  %img_#{$name} {
    background-image: url("#{$dir}/#{$name}.svg")
  }
}

@include img("sprite", "images/sprites");
@include img("animation", "images/one-off");

.error {
  @extend %img_sprite;
}