Update Document and Image Content Control

During an Update Document action when I attempt to set an Image content control in a Word Document, the image text is updating, but not the actual image in the document.

Content control title: ImagePreview

value: http://is2.pens.com/is/image/NationalPen/CTR-LAV

 Any insight into how to get the image to update would be appriciated.

 Thanks,

Mike Boyken