Assumes you have a png fallback image of the same name (different extension).

SVG background with PNG fallback

@mixin svg-background($image) {
  & {
    background-image: image-url("#{$image}.svg");
    background-position: top left;
    background-repeat: no-repeat;
    background-size: contain;
  }
 
  .no-svg & {
    background-image: image-url("#{$image}.png");
  }
}