Once the engine has support for modded graphics files, it'd probably be useful to have the editor support some kind of "graphics library" function, where people could mix-and-match from preset libraries of graphics. For instance, the Book III graphic images would be the "base" set, but you'd be able to load up the Book II graphic library and pull some (or all, if there's room) of those into the file for use in a mod. Presumably you'd want to do this for both the item and tile graphics.
Once the engine has support for modded graphics files, it'd probably be useful to have the editor support some kind of "graphics library" function, where people could mix-and-match from preset libraries of graphics. For instance, the Book III graphic images would be the "base" set, but you'd be able to load up the Book II graphic library and pull some (or all, if there's room) of those into the file for use in a mod. Presumably you'd want to do this for both the item and tile graphics.