Image Copyright Concern & Etiquette.. by: Aaron Barnhart
There is no need to acknowledge any artist of a public domain artwork unless you want to. Furthermore, your transformative use would be acceptable under copyright law as fair use — a landmark case involved copyrighted Grateful Dead posters (google Bill Graham Archives v. DorlingKindersley Ltd.).
Everyone who self-publishes owes it to themselves to understand the fast-changing world of fair use. *Reclaiming Fair Use* by Aufderheide and Jaszi is the best review of this subject. Jaszi has a nice summary of BGAv. DK on page 7 of this:
Aaron Barnhart’s new book: Take a ride on The Big Divide! http://thebigdivide.com/