-images
index.html
sources.js
<html>
<head>
<meta charset="UTF-8">
<script language="javascript" type="text/javascript" src="sources.js"></script>
</head>
<body>
</body>
</html>
document.addEventListener("DOMContentLoaded", function(event) {
var img = new Image();
img.src = 'images/background.bmp';
document.body.appendChild(img);
});