title: Show image instead of checked state of checkbox in extjs
body: <p>How to show a image (ticked image) instead of the default tick of checkbox when the user checks it? </p>
  
  <p>I tried using <code>checkedCls</code> config, in which the image is coming but backside of the checkbox.</p>
  
  <pre><code>checkedCls: 'checkedBoxStyle'
  </code></pre>
  
  <hr>
  
  <pre><code> .checkedBoxStyle{
         background-image:url('http://www.chathamhouse.org/sites/default/files/public/images/buttons/tick-icon.png');
         background-repeat:no-repeat;
   }
  </code></pre>
  
  <p><a href="http://jsfiddle.net/nue7j/4/" rel="nofollow"><strong>jsfiddle</strong></a> to start.</p>