The foreign Amazon sites all seem to use the same method; the only difference is that instead of starting with the http://images.amazon.com/ domain, the amazon.jp images start with http://images-jp.amazon.com/ while the amazon.co.uk and amazon.de images start with http://images-eu.amazon.com/ - Amazon.ca uses the same domain as Amazon.com.
http://images.amazon.com/images/P/0762423374.01._PE20_SCMZZZZZZZ_.jpg
http://images.amazon.com/images/P/ - doesn't vary. That points to the right place on the Amazon servers.
0762423374 is the ASIN, the identifier that Amazon uses for every item it stocks.
01 is an odd duck of a field. It selects the image and the format of the percentage off bullet.
_PE20_SCMZZZZZZZ_ gives information on the size of the image and adornments added to the image. I've found three formats that this field can have.
