Where does Photo Booth 6.0 store its photos?

We are on our fourth iMac... a brand-new 27" 3.2 GHz i5.

We have Mavericks (OS X 10.9.4).

We have Photo Booth.

It's nice to see that the new Photo Booth shows us both the photos we've taken on this new iMac, and the ones from the last iMac.

I do still have pictures from our "original Photo Booth," dating back to 2007.

I would like all of our Photo Booth photos, from 2007 through just now, in one location, all visible within Photo Booth.

It looks like the photos for Photo Booth 6 are stored under the Pictures library: Pictures / right-click on Photo Booth Library / Show Package contents / Pictures -or- Originals.

When I copy any of the pictures from ~ 2007 into that folder, they are in the folder but don't show in Photo Booth itself.

This makes me think there is some config file that just needs to know to look for the other, older photos.

Ultimately... how can I get the current Photo Booth on the current iMac to show the pictures we took in Photo Booth from iMacs # 1 & #2 (as #3 did copy over when we upgraded machines)?

Thanks,

Michael

P.S. I realize this is a Photo Booth question, posted to an iPhoto Community; I do not see any Photo Booth options in the Community list. Thanks.