XBMC4Xbox

From time to time I clear my thumbnails folder to prevent it from getting bigger than the Ghostbuster's marshmallow monster , but when I do that I lose all my fanart. So I was wondering if it would be a good feature to separate library fanart (backgrounds, banners, posters, etc.) from the rest of the thumbnails.

I'm not 100% sure on this but I have a feeling Dans thumbnail cleaner might give you the option of what you want to clean. I think I have it available in XAI in the "Misc" section, failing that it's definitely available on SVN Repo Installer.

Yeah, the post is gone with old forum, but yes the plugin should be available in SVN Repo Installer > xbmc4xbox-addons repository.
https://code.google.com/p/xbmc4xbox-add ... Thumbnails

I think he's removing all thumbnails - well, when you do that, just don't remove the FanArt subfolder or use the plugin, it should clean only entries that cannot be found in your library.