I stumbled upon Earth Album, a great map mash-up that bills itself as "a simpler, slicker Flickr mash-up that allows you to explore some of the most stunning photos in the world courtesy of Google maps and Flickr. " This is very true. Look at these photos of Lhasa. A ribbon of photographs pops up whenever you zoom into any area on the map.
The Panoramio photos in Google Earth give a nice picture of what's on the ground in Lhasa as well. There seem to be hundreds of photographs taken in Tibet located in Google Earth's Panoramio layer.
Whether the trip to Tibet will go as planned and whether I can handle the altitude once there are other questions, but it's nice to get a feel for the place before taking off.