Yes, you can use the kj_magemail_product_image_fetch_after observer to fetch the image URL and modify it.
Here’s a quick example of the observer setup in config.xml:
<global>
<events>
<kj_magemail_product_image_fetch_after>
<observers>
<namespace_kj_magemail_product_image_fetch_after>
<class>KJ_MageMail_Model_Observer</class>
<method>productImageFetchAfter</method>
</namespace_kj_magemail_product_image_fetch_after>
</observers>
</kj_magemail_product_image_fetch_after>
</events>
</global>And the observer:
<?php
/**
* @param $observer Varien_Event_Observer
*/
public function productImageFetchAfter($observer)
{
/** @var Varien_Object $data */
$data = $observer->getData('data');
/** @var Mage_Catalog_Model_Product $product */
$product = $observer->getData('product');
/**
* The product ID that was requested in the product image URL.
* This may be different from the $product model, because the $product
* model attempts to load a product that has a small_image set on it,
* and if it doesn't have one, it will load the parent product.
*/
$requestedProductId = $observer->getData('requested_product_id');
$data->setData('image_url', 'http://local.magemail.co/app/media/uploads/d2176f2e5d09f7071cf98ea460f0b9b6.png');
return $this;
}