The solution was extremely simple, so it might be worth adding to 2.0.
Pretty much just a drop in class.
I used the extended CRichEditCtrl from here
http://www.codeproject.com/KB/edit/COleRichEditCtrl.aspx
I just make it a member of RTFConcatenator and use that instead of
the plain hidden RICHEDIT50W control created in the constructor and
set m_hWnd the created COleRichEditCtrl.
The only other bit I had to change was comment out the check in
RTFConcatenator::CollectCallback that checks if (nChars > 0) because
images are not characters.
But other than that everything works the same except now I can get
images in my exported RTF.
This might be something you would be interested in adding...