Hi, I'm trying to understand how can I do to let my site be reachable from google image search spiders. I like how last.fm solution, and I thought to use a technique like his staff do to let google find artists images on their pages.

When I'm looking for an artist and I search it on google image search, as often as not I find an image from last.fm artists page, I make an example:

If I search the band Pure Reason Revolution It brings me here, the artist's image page
http://www.last.fm/music/Pure+Reason+Revolution/+images/4284073

Now if I take a look to the image file, i can see it's named:
http://userserve-ak.last.fm/serve/500/4284073/Pure+Reason+Revolution+4.jpg
so if I try to undertand how the service works I can try to say:
http://userserve-ak.last.fm/serve/ the server who serve the images
500/ the selected size for the image
4284073/ the image id for database
Pure+Reason+Revolution+4.jpg the image name

I thought it's difficult to think the real filename for the image is Pure+Reason+Revolution+4.jpg for image overwrite problems when an user upload it, in fact if I digit:
http://userserve-ak.last.fm/serve/500/4284073.jpg
I probably find the real image location and filename

With this tecnique the image is highly reachable from search engines and easily archived.

My question is, does exist some guide or tutorial to approach on this kind of tecniques, or something similar?