It seems that what you are saying is that you want your FileMaker database to dynamically reference the photos in your iPhoto library folders, that you do not want to "embed" the photos in the database itself. What you would need to do that is the file paths to the photos. iPhoto stores all the file paths to the photos in an "album" in a file, AlbumData.xml, which is in a known location in your user folder, Pictures folder, iPhoto Library folder.
On my computer it looks like:
Macintosh HD:Users:fej:Pictures:iPhoto Library:AlbumData.xml
In FileMaker syntax this would be:
filemac:/Macintosh HD/Users/fej/Pictures/iPhoto Library/AlbumData.xml
This can be calculated from within FileMaker.
In the AlbumData.xml file there is an image path and a thumb path, so those are the 2 to import. You need a fairly simple XSL stylesheet in order to pick them out of the xml. I've uploaded a file to my web site which should work. It has 2 scripts. The 1st one imports from a fixed file path, so it will not work for you until you change the path to match yours. The 2nd script (which is visible) dynamically calculates your path, using Get (DesktopPath) to get your hard drive and user name.
If you have multiple iPhoto albums or other items in there (movies, etc.), well, I don't quite know. I have a simple folder myself.
Thanks for your reply. I will need time to digest this and to see if I understand it and do it.