Replace the image on checkout with the proper image for your SSL certificate.
<?php
/*
 * Plugin Name: Easy Digital Downloads - Add Security Info to Checkout
 * Description: Replace the image on checkout with the proper image for your SSL certificate.
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function pw_eddwp_add_security_info() {
?>
	<a href="https://www.PositiveSSL.com" id="ssl-seal" title="SSL Certificate Authority" style="font-family: arial; font-size: 10px; text-decoration: none;">
		<img src="https://www.positivessl.com/images/seals/PositiveSSL_tl_trans.gif" alt="SSL Certificate Authority" title="SSL Certificate Authority" border="0"/><br>SSL Certificate Authority
	</a>
<?php
}
add_action( 'edd_after_cc_expiration', 'pw_eddwp_add_security_info' );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.