The "On Sale" graphic is an HTML image that can be used to visually indicate when an Item's price has been further reduced by an additional CyberStore (or web) discount. You can specify a custom graphic location by setting the OnSaleGraphicPath property to any valid, resolvable URL.
If the Item does not include a CyberStore web discount, then the "On Sale" graphic will never show, even when the ShowOnSaleGraphic property is set to a value of true.