Now, I am under NDA regarding Leopard but I'm not under any NDA about iLife and the existence of ImageKit is public knowledge. It's described in Apple's own Leopard Technology Series for Developers:
[ImageKit] makes available powerful imaging services that can be easily incorporated into your application. It provides functionality for finding, browsing, and viewing images in a collection.
iLife's version of ImageKit is hidden away inside a private framework called
GraphicAppSupport.framework. iPhoto 7 does not link against this framework, but another interesting component of iLife '08, used by most of the apps, does: the
iLifeMediaBrowser.framework. This appears to be the Media palette used in several Apple applications. I don't know if the questions themselves were under NDA during the Aqua Feedback session at WWDC, but Dan Wood should be approaching happier. I don't think I've seen this framework before.
There was a rumour some time ago that iLife '08 depended on Leopard and this explained its non-appearance at MacWorld in January. Unless the ImageKit backport was always part of the plan for delivering iLife '08 on Tiger, this suggests that those rumours had some credence.