I can't speak for music, but otherwise the only change I'm aware of is that you can no longer change the contents of the GlobalLoad.txt file.
There is still
another method for loading Luclin models (by shuffling the contents of data files around so the Luclin models are inside data files that
are in globalload already). Haven't seen any official word if this is "legit", although some forumgoers are, of course, vocally against it.
No verification of the contents of data files appears to be done as far as I'm aware. I haven't looked at textures specifically, but I would be surprised if those are checked considering how much isn't. Should be able to swap texture files in data files that are already loaded, I figure. I hadn't heard anything a transparent wall exploit, but it's interesting seeing as nothing prevents you from flagging an entire zone as transparent, technically:
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That's a Luclin iksar in the corner there btw