app/design/adminhtml/default/default/template/sales/order/view/items/renderer

default.phtml

在</tr>前加入

    <td class="a-right " width="70">
    <?php
$result = Mage::getModel('catalog/product')->load($_item->getProductId());
$_img = '<img src="'.$this->helper('catalog/image')->init($result, 'thumbnail')->resize(70).'"/>';
    echo '<a target="_Blank" href="'.$this->helper('catalog/image')->init($result, 'thumbnail')->resize(300).'">'.$_img.'</a>';
  
?>
    </td>