iPhoto: what remains when you delete every image?

I'm working on a peculiar iPhoto 6 bug, and one of my experiments meant I deleted every image in a 11.5GB iPhoto Library. I was surprised to find that, with every image deleted, the empty Library was 792MB.

I dissected the remainders until I got the empty Library to 5.8MB. Here's what remained:

Thumb*.data: 125MB - when you delete images iPhoto does not necessarily clean up the thumb caches. These can be safely deleted.

iPod Photo Cache: 580MB - this is what goes on my iPod. It wasn't removed when I deleted all the iPhoto images.

2004: 75MB (41 photos)
and
2005: 2.3MB (1 photo)

I think these are left over folders from when I moved from iPhoto 5 to iPhoto 6. They probably hold images that remained after everything else was relocated. Interestingly iPhoto never produced any error messages about these residual images. I think they were all images I deleted that somehow didn't get removed properly.

Originals: 2 photos only remained in my Originals folder, apparent duplicates two of the images in the 2004 folder.

The final residual: 5.8MB

I'm going to take the 45 images I recovered and compare them to the images in my main Library. I'll provide as an update to this post.