Virtuemart : Add Payment Method Image

administrator/components/com_virtuemart/classes/ps_payment_method.php

echo "<label for=\"".$db->f("payment_method_name")."\">".$db->f("payment_method_name");
to

echo "<label class=\"method_".$db->f("payment_method_id")."\" for=\"".$db->f("payment_method_name")."\">".$db->f("payment_method_name");

Added a CSS class to <label> which uses payment_method_id as identifier. You just have to add styling to your css file.

label.method_4 {background:url("https://cms.paypal.com/cms_content/US/en_US/images/developer/AcceptanceMark_60x38.gif") no-repeat 0 20px transparent;