Back in 2005 I was trying to accurately geocode a bunch of photos I'd taken at the excellent Eden Project, but found at the time that the Google Earth imagery of the area showed little more than a quarry. I made a series of overlays from bits of more detailed and more up-to-date maps and finished off by aligning the map images from the guide book. These are a little out of date, but I thought they would be worth sharing.
The guide book images are used with the kind permission of Mike Petty, the Eden Project Publishing Manager.
I've left the two biome images hovering in the air and applied some transparency, which produces a pleasing effect.
Transparency and altitude offsets seem to be only very rarely used. I'm sure there are plenty of practical and artistic effects that could be generated by them - I think I will have to experiment.