I've made panorama's with historical image overlays, using distortored hotspots, a very nice effect:
http://weblab.ab-c.nl/verrijkte-panoramas (Dutch text; hover the panorama's)
There's also a post on my panorama's on How to be a Retronaut, with English texts:
http://www.howtobearetronaut.com/2010/12/augmen…lity-panoramas/