My code for SVG covers (probably equivalent to JSWolf's one), adapted to your image size:
Code:
<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ops="http://www.idpf.org/2007/ops" xml:lang="en">
<head>
<title>Cover</title>
<style type="text/css">
@page, body.cover { margin: 0; }
div { text-align: center; }
</style>
</head>
<body class="cover">
<div>
<svg version="1.1" xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink"
width="100%" height="100%" viewBox="0 0 600 900"
preserveAspectRatio="xMidYMid meet">
<image width="600" height="900" xlink:href="images/Cover.jpg" />
</svg>
</div>
</body>
</html>