By default, Magento does not report or delete unused product images. With unused product images, I mean images that you can find in the directory "media/catalog/product" and not assigned to any existing product.

Here is what you have to do to automatically delete all those images

• Install the Image Clean Extension
• Create an external file called imgClean.php with the content - Listing 1
• Update class Mage_Imaclean_Model_Mysql4_Imaclean_Collection : add a new method called getImagcleanIds with the content - Listing 2
• Automate the deletion of unused images using automated tasks (cron jobs)

<?php

require_once 'app/Mage.php';

umask ( 0 );

$currentStore = Mage::app ()->getStore ()->getId ();

Mage::app ()->setCurrentStore ( Mage_Core_Model_App::ADMIN_STORE_ID );

Mage::helper('imaclean')->compareList();

$imacleanIds = Mage::getModel('imaclean/imaclean')->getCollection()->getImagcleanIds();
 

 
    $model = Mage::getModel('imaclean/imaclean');

    foreach ($imacleanIds as $imacleanId) {

		$model->load($imacleanId);
                unlink(Mage::getBaseDir ( 'media' ).DS.'catalog/product'. $model->getFilename());

		$model->setId($imacleanId)->delete();

    }
	
	Mage::app ()->setCurrentStore ($currentStore);

<?php

public function getImagcleanIds() {	
	   $array=array();	
	   try {   
	       $coreResource = Mage::getSingleton('core/resource');	
		   $write   = $coreResource->getConnection('core_write');
		   $imacleanTable  = $coreResource->getTableName('imaclean');
		   $sql = "SELECT * FROM " . $imacleanTable;
		   $read = $write->query($sql);
		   while ($row = $read->fetch()) {	
		   $array[]   = $row['imaclean_id'];
		   }	
	    }catch(Exception $e){
     		Mage::log($e->getMessage());
		}						
		return $array;	
     }