Try the following steps:
Replace your image code file with the following:
<?xml version='1.0' encoding='utf-8'?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>part0003</title>
<link href="../stylesheet.css" rel="stylesheet" type="text/css"/>
<link href="../page_styles.css" rel="stylesheet" type="text/css"/>
</head>
<body class="calibre-cover">
<div class="image">
<img alt="cover" src="image_rsrc2GE.jpg" class="calibre3a"/>
</div>
</body>
</html>
Add the following to your stylesheet.css file:
.calibre3a {
height: 100%;
width: 100%;
}
.calibre-cover {
display: block;
padding-left: 0;
padding-right: 0;
text-align: center;
margin-bottom: 0;
margin-left: 0;
margin-right: 0;
margin-top: 0;
}
.image {
display: block;
text-align: center;
padding: 0;
margin: 0 0;
}
Copy the following to a blank file and save it as page_styles.css. Add the page_styles.css file to your epub file (Ctrl-F5):
@page {
margin-bottom: 5pt;
margin-top: 5pt;
}
After you've done the above steps, right click on the image html file and click "Link Stylesheets."
Let me know what happens with your cover image.