html,
body {
  margin: 0;
  padding: 5px;
  font-family: Verdana, sans-serif;
  background-color: lightblue;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

#button{
  background-color: black;
  height: 10px;
  width: 10px;
  position: fixed;
  top: 0;
  left: 0;
}

body::before,
body::after {
  content: "";
  position: absolute;
  margin: 5px;
  top: 0;
  width: 150px;
  height: 150px;
  background-size:contain;
  background-repeat: no-repeat;
}

body::before {
  left: 0;
  background-image: url(https://cdn.britannica.com/78/6078-004-77AF7322/Flag-Australia.jpg)
}

body::after {
  right: 0;
  background-image: url(https://logowik.com/content/uploads/images/macquarie-university5860.jpg)
}