img.bg {
  min-height: 100%;
  min-width: 1024px;
  width: 100%;
  height: auto;
  pointer-events: none;
  position: fixed;
  top: 0;
  left: 0;
}
@media screen and (max-width: 1024px) { /* Specific to this particular image */
  img.bg {
    left: 50%;
    margin-left: -512px;   /* 50% */
  }
}