Donavon West has created a killer deep zoom using tens of thousands of images making up the face of Barack Obama.
It is very cool and available to view at http://www.deepzoomobama.com
The great part is that Donavon has also released a "how to" build your own mosaic and host it on us for free using Silverlight Streaming.
MultiScaleTileSource check out their DeepEarth project.
They have Open Source'd it - http://www.codeplex.com/deepearth
So you have all you need go make your own Mosaic and post it in the comments below.