The Image Watermark v1.0 plugin is now available for Quick.Cart version 1.0 or greater.

 This plugin puts a watermark image on displayed images, without affecting the image stored on file. It can be configured for Product images, and/or Content/Category images. It can also be set to include or exclude thumbnail images, with provision for a different watermark on the thumbnails.

You can read more about it in this document (opens in new window). 

Please note that it will only run under Plugin Manager (v2.0) .