<h1>The div is set to 10px high only so html/body are not stretched</h1>
<div>
  <p>test</p>
  <p>test</p>
  <p>test</p>
  <p>test</p>
  <p>test</p>
  <p>test</p>
  <p>test</p>
</div>

body {
  margin: 0;
  background: url(https://picsum.photos/200/1400);
  background-repeat: no-repeat;
  background-size: 100% 100%;
}
h1 {
  margin: 0;
  font-size: 50px;
  background: red;
  text-align: center;
}
div {
  height: 10px;
}