The Product table needs two additional fields that reflect on the product detail page. UPC code and ASIN #.
UPC code is important for Googel searches.
ASIN #: Amazon Store ID # - is also useful. I add the ASIN # to all my products so that when someone does a search for the ASIN #, it not inly shows up under Amazon, but my store as well.
nopCommerce does not have a field for ASIN. But it already has a "GTIN (global trade item number)" field. You can use it for UPC (in North America), EAN (in Europe), JAN (in Japan), and ISBN (for books).
You already can specify GTIN (override a default one at the product level) by going to product details page > product attributes > attribute combination > add/edit combination