Earlier quoted context omitted.
I read somewhere that stolen works of art are used as a form of currency between drug crime Organisations
Doesn't make a ton of sense. If you can't convert it to currency easily, why does it have value at all?
The whole point of currency is that it doesn't have to have value at all. You use it for goods and services. Money doesn't have value, it's just a piece of paper, bitcoin is just bunch of bytes in a linux server. This is also why people used use gold as currency; it's not that gold is a very practically valuable metal (say, unlike iron) but it was the currency mostly because it wasn't too common, but also not rare enough to make it impractical to use for goods and services.