#background {
background-image:url('http://birsmatt.ch/de/wp-content/uploads/2016/04/bg_left.png');
background-position:left;
background-repeat:no-repeat;
height:100%;
width:100%;
z-index:1;
position:absolute; /* make it overlap your website content */
}
<body>
<div id='background'></div>
<div id='rest of your content'>
...
</div>
</body>
body:before
。 - isherwood<div id='background'></div>
? - ScemuFessa