Databases Design startup

Database Design Problem

A few weeks ago, I had to work out a database design for my startup. I had a bit of a hard time deciding on a design direction, but after thinking about it, I settled on a design I was happy with.

While I was still making up my mind, I discussed the problem with a couple of friends, and to better describe the problem and the proposed solutions I wrote up a short document describing them. I decided to publish this document along with my choice and considerations. Maybe someone else will benefit from my choice, or at least from the alternatives I listed.

Problem description:
We want to to have a table with collected information from various sources.

For example, let’s say we want to collect information about paintings. We’d want to have a database holding for each painting we know about its dimensions, painter, description, link to an image file, etc. Since we collect this information from various sources (maybe harvest information from multiple websites), we would like our application to display each field either from all sources, or from the best source available.
(Note: in my original formulation, being able to display the value from the best source was enough).