Magento sale watermark
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Due to being a new to Magento world, I have limited understating of its coding pattern.

I have created a cart price rule which works fine. However now I want to show the sale watermark image on product listing page making product on sale more prominent for customers. This sale watermark must not be displayed when sale period is over. 

My approach is as below

1. Modify the cart price rule form to let admin to upload corresponding sale water mark. Then update list.php to determine the rule and then add sale water mark image to product list.As cart price rule specify the sale dates, I am assuming after due date rule would become inactive and image would not get displayed.

However before i start coding for it, I am wondering if someone has easier approach.

