Call upon image in external HTML object

I've got an external HTML object which bookmarks a particular URL in a course published to HTML. It's working great with text, but I'd like to direct users to click an image to set the bookmark... what URL do I use for an image in the course? Here is the HTML I'm using to set the bookmark... I need to replace the all-caps/italics portion to insert an image with the file name, "bookmark.jpg":



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