How is album art stored in ALAC tags?

When I opened a single tag today in order to edit it, the album cover did not show up in either the "Summary" or "Artwork" tabs, even though it showed up in the lower right hand corner of iTunes. I then started checking other tracks and found they were all like this.

I have just started the process of importing my CD collection in ALAC. To add album art, I have been selecting all of the songs in one album, then dragging and droping the art from Firefox (Amazon, Google Image Search, Etc.) on to the "Drag Album Artwork Here" in the lower left hand corner of iTunes. It takes a moment to apply the artwork to all of the tracks, then the album cover appears in the lower left hand corner for whichever track I click on... like normal.

I'm assuming since the artwork always shows up in the lower right hand corner that it is being saved in the tag.

Is this just an UI quirk? Is this normal iTunes 6 behavior? Could it be because I'm using high quality artwork at 600x600 resolution whenever possible?

I'm ripping for archival purposes right now... and it's important to me that the artwork is correctly saved.

For starters I have very limited knowledge of this as I have only toyed with it a bit.
I do know that the album art is kept in the tags, as you can move the individual files to another computer, and the art remains (in itunes). However it is handled differently from the aac tags, as external (from itunes) programs can often see the aac tags, but not that alac tags. It appears that for now itunes is the only program that handles alac tags in this way, and as a result I decided to go with a different lossless format.