body {
  background-image: url("https://wallpapercave.com/wp/wp5189736.png");
  background-repeat: repeat;
  background-size: 200px;
  animation: scrollbg 6s linear infinite;
}

@keyframes scrollbg {
  from {
    background-position: 0 0;
  }
  to {
    background-position: 200px 200px;
  }
}