This addon adds a sale banner to the image of every product having a current special. The banner is an image overlay, so it can be any shape or size (smaller than the product image of course).
The code recognizes the store language in use and selects a sale banner in that language. This allows the freedom to design a banner suited to each language in the store.
There's a screenshot available if you want to see what it can look like. Of course you can use a different image as the overlay.