This sounds like a cool project! I’ve considered making a “Catacombs of Uzkulak” expansion to Warhammer Quest Silver Tower since I was able to gateway friends into the hobby with that game.
This post on my blog links to various doodlings I’ve done. I’m not sure if the style will align with your vision or theme but perhaps with some clever cropping something might be there. They’re plain ink pen with no color, akin to an historians notebook. Happy to let you integrate them in some manner with mayhaps just a footnote of credit somewhere in your tome.
Cheers