As I noted over on RPGGeek about this matter, anyone who has questions about art use (or any other rights or payment issues), he can contact me at James@Chaosium.com. It would be helpful if anyone making a claim can provide copies of original contracts and communications with Chaosium or other companies.
The new management of Chaosium has been very public about getting old problems resolved. These efforts have been covered in the hobby press quite prominently. https://geekandsundry.com/cthulhu-company-kickstarted-itself...
executive editor, Chaosium