We're just a marketplace, like Etsy or Ebay behind the scenes.

That being said, I have personally visited many of the sellers and for advanced products such as highly detailed portrait paintings (the ones sold on Instapainting.com), the artists always work from their home and are independent contractors. It's only for large quantity mass replica work that are actually done in factories, and I've visited those factories as well, however they do not provide the detailed portraits type of work.