Voat/Pizzagate had done a lot of digs on art dealings being used as a cover for human trafficking. As I recall an anon there even found out something about how they are even able to skirt the customs system when transporting "art" from country to country – have their own "special" shipping system that circumvents the process.
Anyway, here is one sampling of a thread. Be sure to read through the comments as there are many good links/connections posted there as well.
https://voat.co/v/pizzagate/1897810