Well. I figured it out after some thinking. In the checkout_2_method.tpl file. I changed the line:
Code:
<td width="80%">{$payment.payment_details}</td>
to
Code:
<td width="80%"><img src="{$ImagesDir}/pm{$payment.paymentid}.png" align="right" alt="{$payment.payment_method}"/>{$payment.payment_details}</td>
Each payment method has a unique id, so I had to name the images using that id number (ex. pm1.png)