Hello,
It looks like the LabVIEW Report Generation Toolkit for Microsoft Office obtains a reference to the "InlineShapes" of the document, then uses the "AddPicture" method of this "InlineShapes" class to add the image to the document.
You may want to consider purchasing the Report Generation Toolkit ...with this toolkit, there is a VI called "Append Image to Report.vi" that takes care of this particular issue for you. Check out
this webpage for more information.
Good luck,
-D