Let's move up to a 4 card version.

<style>
  body {
    background-color:green;
  }
  div {
    text-align:center;
  }
</style>
<body>
  <div>
    <img src='cards/back.png'>
    <img src='cards/back.png'>
  </div>
  <div>
    <img src='cards/back.png'>
    <img src='cards/back.png'>
  </div>
</body>