title: Take product images from cache in admin product grid
body: <p>I have added a new column in admin product grid called images, which shows product images as a thumbnail. My problem is that in very long lists my panel gets slow.
  This column is in a rewrite of Mage_Adminhtml_Block_Widget_Grid, and here is the code:</p>
  
  <pre><code>$this-&gt;addColumn('thumbnail',
              array(
                  'header'=&gt; Mage::helper('catalog')-&gt;__('Thumbnail'),
                  'type'  =&gt; 'image',
                  'width' =&gt; '75',
                  'index' =&gt; 'thumbnail'
      ));
  </code></pre>
  
  <p>Well i need this column to take images resized from cache, can anybody help?
  Thanks</p>