Magento : add thumnail in admin grid

Remember that grid is working fine.Here module is consider as Bd_Collegeprogram

First add the code in the _prepareColumns() function
$this->addColumn("image", array(
                "header" => Mage::helper("collegeprogram")->__("Image"),
                "index" => "image",
                'type' => 'image',
                'width' => '50px',
                'renderer'  => 'collegeprogram/adminhtml_collegeprogram_renderer_image'
                ));
Now create a block as adminhtml_collegeprogram_renderer_image
class Bd_Collegeprogram_Block_Adminhtml_collegeprogram_Renderer_Image extends Mage_Adminhtml_Block_Widget_Grid_Column_Renderer_Abstract{

    public function render(Varien_Object $row)
    {
        $html = '<img ';
        $html .= 'id="' . $this->getColumn()->getId() . '" ';
        $html .= 'src="' . $row->getData($this->getColumn()->getIndex()) . '"';
        $html .= 'class="grid-image ' . $this->getColumn()->getInlineCss() . '"/>';
        return $html;
    }
}