There is a private media option in the latest patch to FTM 2012. I have not tried it yet.
From the update description:
"2. Private Media - Media items can be marked private and will be excluded from TreeSync."
Edit: if you post on the FTM board, you might get help from the power users who frequent that board. http://boards.ancestry.com/topics.software.famtreemaker/mb.a...