Hello and thank you for your comments regarding the artwork. I am, in fact, the artist responsible for creating the splashscreen, illustrations, and interface art for Avernum 6. I've been doing the art for Jeff's games starting around Avernum 5; before that, I think it was done primarily by an artist named Andrew Hunter.
You can see my online portfolio at:
http://www.benresnick.com/
-Ben Resnick