.img {
  background-image: url(images/2019_updates/banners/Homepage_Blue_wText.jpg); 
}
@media 
  (-webkit-min-device-pixel-ratio: 2), 
  (min-resolution: 192dpi) { 
  .img {
    background-image: url(images/2019_updates/banners/Homepage_Blue_wText_mobile2.jpg);
  }
}