You didn't find that construction on my web site. What you may have found is

{INCLUDEPICTURE {IF TRUE "{Mergefield Path}{Mergefield Image}.jpg"} \d }
or in your case
{INCLUDEPICTURE {IF TRUE "{Mergefield PhotoPath}Blank.jpg"} \d }

This requires that the image is present at the path set in {Mergefield PhotoPath}. To add the conditional field, that must go outside the construction thus

{ IF {Mergefield PhotoPath} <> "" "{INCLUDEPICTURE {IF TRUE "{Mergefield PhotoPath}Blank.jpg"} \d }" "" }

Mergefield Photopath must return "Q:\\Path\\" without the filename

See also http://www.gmayor.com/mail_merge_graphics_addin.htm

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Graham Mayor - MS MVP (Word) (2002-2019)
Visit my web site for more programming tips and ready made processes www.gmayor.com