Two marvelous links with ballad illustrations:

The Bodleian Library's collection - http://www.bodley.ox.ac.uk/ballads/ballads.htm has scanned images from authentic broadside ballads. 'Bonnet so Blue' is illustrated on the link above, but there are many more in the searchable database, apparently.

George Wharton Edwards - http://www.sacred-texts.com/neu/eng/boeb/ beautiful wood-cut illustrations for over twenty songs, from 'Fair Margaret' to 'The Twa Corbies'.







You might also try the art of Tom Canty - contemporary book illustrator