body.function-login {
  background: url('https://cdn.pixabay.com/photo/2015/06/08/15/11/typewriter-801921_960_720.jpg') no-repeat fixed center;
  background-size: cover; 
}

body.function-menu {
  background: url('https://cdn.pixabay.com/photo/2015/06/08/15/11/typewriter-801921_960_720.jpg') no-repeat fixed center;
  background-size: cover; 
}