Fallback to PNG if SVG is not supported. Note: of course, you must create the PNG version of the SVG image. Reference: http://toddmotto.com/mastering-svg-use-for-a-retina-web-fallbacks-with-png-script/

functions.js

( function( $ ) {
  
  $( window ).load( function() {

    function supportsSVG() {
      return !! document.createElementNS && !! document.createElementNS('http://www.w3.org/2000/svg','svg').createSVGRect;
    }
    if (!supportsSVG()) {
      var imgs = document.getElementsByTagName('img');
      var dotSVG = /.*\.svg$/;
      for (var i = 0; i != imgs.length; ++i) {
        if(imgs[i].src.match(dotSVG)) {
          imgs[i].src = imgs[i].src.slice(0, -3) + 'png';
        }
      }
    }

  }

} )( jQuery );