title: wrap exist element with an image as background
body: <p>I have some containers in the page like this:</p>
  
  <pre><code>&lt;div id="con1" class="window"&gt;
      &lt;div&gt;xxxx&lt;/div&gt;
      &lt;div&gt;xxxx&lt;/div&gt;
  &lt;/div&gt;
  
  &lt;div id="con2" class="window"&gt;
      &lt;div&gt;xxxx&lt;/div&gt;
      &lt;div&gt;xxxx&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And an image like this:</p>
  
  <p><img src="https://i.stack.imgur.com/6pCdw.png" alt="enter image description here"></p>
  
  <p>Now,I want to make the image as the background of the containers to make the containers look like a window. Like this:</p>
  
  <p><img src="https://i.stack.imgur.com/FL0PB.png" alt="enter image description here"></p>
  
  <p>Also,the size of the containers may changed according to user. So I want it can auto expand when the content of the containers added.</p>
  
  <p>Any idea?</p>
  
  <hr>
  
  <p>update:</p>
  
  <p>What I have tried yet:</p>
  
  <p><img src="https://i.stack.imgur.com/R1Zg3.png" alt="9 divs layout"></p>
  
  <p>And this is what I get now: <a href="http://jsfiddle.net/TqutW/" rel="nofollow noreferrer">jsfiddle</a></p>