While I haven't had the occasion to use it yet, there is the 'http://skyrim.nexusmods.com/mods/19337' over on the Skyrim Nexus site. Works with Oblivion as well.
This utility finds the duplicate textures in up to 3 folders (the first one being the reference/vanilla folder). The duplicate textures can then be viewed side-by-side with file size and dimensions info. You can specify how many folders you are comparing when starting a new session.
Might be handy if you are looking at conflicting references and trying to pick one.
-Dubious-