Thank you! According to current copyright laws the buyer does not hold copyright to the artwork.

What does current law have to do with it? Works for hire are generally copyrighted by the hirer, and copyrights can be transferred by contract.

Just to add a bit of (useful) pedantry - what happens to copyright depends on the jurisdiction. In some (Norway, for instance) you can not fully transfer all rights, even if you want to. (This _is_ pedantry, as you can pretty much transfer any commercial rights - just about the only thing you can not transfer is the right to be named the creator of the work.

It's kind of true that you can't transfer all rights in the US, where while you can nominally transfer all rights, any such transfer can be reclaimed 35 or 40 years, with the required notice of he reclamation provided after 25 or 30 years.

IIRC/IANAL, in Germany you are allowed to transfer commercial use and declare any different name as the creator. But you can't transfer the copyright itself, so you will always stay in control.

The painting is also a derivative work.