Demo

style.css
index.html

body { font-family: sans-serif; }

body, section { padding: 20px; }

section {
	background-image: url("tim.jpg");
	background-size: cover;
}

h1 { font-size: 400%; }

<!DOCTYPE html>
<html>
	<head>
		<meta name="viewport" content="width=device-width, initial-scale=1">
		<link href="/assets/styles/reset.css" rel="stylesheet">
		<link href="style.css" rel="stylesheet">
	</head>
	<body>
		<section>
			<h1>This is a heading</h1>
			<p>And a paragraph, to have some text over the image and also to define the size of the section/parent.</p>
		</section>
	</body>
</html>