The painting was done by New England artist John Thompson (I once tried to contact him through his official site, http://www.johnthompson-artist.com, and here is what he had to say about it: "It was done for the second movie in the series. I don't remember who commissioned it though. It wasn't used
The concepts were done by John Bloomfield (http://www.us.imdb.com/name/nm0089278/), who was the costume designer on Conan
. That's his signature between Subotai's feet.
As for stills from the DVD, Protoplasme did those screenshots some time ago (for educational purpose only!