The sad part is that it's only textures, so currently no morphs/model changes will work. Still, for those of you who like changing your gear and weapons can still have some fun with this.
You need to dig up your old .mpq files for this, because it works similarly as to how it did pre-4.0.1. They need to be uncompressed.
Rename the .mpq texture edit you want to use to SoundCache-3
Go to your WoW > Data > Cache folder and remove the SoundCache-3 file that is currently there (and I suggest putting it in a safe spot so you can put it back before Cata goes live) and then replace it with your custom mpq file and it should work.
Good news is, this also means your nude patches will work, but due to Blizz's meddling they seem to look slightly lower quality than they used to be and I haven't been able to get around that.
I can't promise that all of your old .mpq edits will work, if they contain any sort of morph/model change edit inside of them, you will crash. But if all your editing is textures, then they should work fine. Feel free to play around and tell me if you find anything or if I'm not being very clear.
http://www.mediafire.com/?rd2511pr717i7bd
^^ Working nude patch for 4.0.3