Short answer: no, it is not possible as a novice user.
I don't know if it is even possible for an expert user. Numbers is not a database app that can show webpages in frames or to query websites for data (other than the built-in functions that go through Yahoo Finance to get stock and currency prices). It might be accomplished with scripting but I am not aware of anything that has been written to take either a snapshot of a webpage for a cell background image or to query a website for the price of a product. I assume with the frequency of changes to websites that anything written would only work for a short time.