The following resources were suggested by Paul Barnaby, Project Officer for the Walter Scott Digital Archive, which draws upon the collections of Edinburgh University Library.
1) Walter Scott Image Collection (Paul Barnaby):
This is an image library of just over 1000 illustrations to the works of Walter Scott and other Scott-related publications. It is part of a larger site, the Walter Scott Digital Archive.
2) Illustrating Scott: A Database of Printed Illustrations to the Waverley Novels, 1814-1901 (Peter Garside and Ruth McAdams):