One of my favorite caricatures of Hayek and Keynes was used on the cover The Hayek-Keynes Debate: Lessons for Current Business Cycle Research (1999). If my memory is correct, Fred Glahe (co-author) discovered the drawing in an issue of The Economist somewhere in the mid to late 1990s. We tracked down the artist and received permission to use the drawing on the cover to which we owe a grateful debt to the now deceased creator Ismael Roldan.
The cover can be seen here.
Unfortunately the newer (cheap) paperback reprint lacks this great piece of art.
For the story on freeing the book from IP limbo see here.
It would be great if someone could free the drawing from IP limbo as well so it could be more widely used.