body {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  height: 100%;
}
body:before {
  content: "";
  position: absolute;
  background: url(/home/bg.png);
  background-size: cover;
  z-index: -1; /* Keep the background behind the content */
  height: 20%;
  width: 20%; /* Using Glen Maddern's trick /via @mente */

  /* don't forget to use the prefixes you need */
  transform: scale(5);
  transform-origin: top left;
  filter: brightness(55%);
}

.logo {
  background: url(/home/logo.png);
  background-size: cover;

  height: 100px;
  width: 140px;
}