The Reluctant Admiral scenario has many modifications to Ship-Art, Plane-Art, and various Load Screens. The modified Ship and Plane Art files are necessary for the scenario and must be downloaded and installed along with the scenario files. RA 4.0 Plane Art.zip and RA 4.0 Ship Art.zip are necessary files for The Reluctant Admiral to present itself correctly. RA 6.0 has some additional ship art for the Japanese B-64 Class Command Cruiser and the experimental CLV Charlotte (Flightdeck Cruiser).
The modified Load Screens and Naval Combat Screen add some real spice to the presentation. Although not required for the scenario to show itself correctly, they are nevertheless some nice pieces of "eye candy" that serve to indicate the scope and intent of this particular mod. You will find these files in the Load Screens download as well as the 6.3 Art Zip File.
Although the scenario has been updated to the version 6.6 since, none of the fixes involve the art files. Their 4.0 versions are fully compatible with 6.4.