https://www.w3schools.com/cssref/pr_...d-position.asp

body {
background-repeat: no-repeat;
background-attachment: fixed;
background-position: center;
background:url("images/1.jpg");
animation:image 5s infinite alternate;
-webkit-animation:image 5s infinite alternate;
-moz-animation:image 5s infinite alternate
}

body { 
  background-repeat: no-repeat;
  background-attachment: fixed;
  background-position: center; 
  background:url("images/1.jpg");
  animation:image 5s infinite alternate;
  -webkit-animation:image 5s infinite alternate;
  -moz-animation:image 5s infinite alternate
}