A BSA file goes to the main Data folder, and it wraps up all the textures in one file (useful with big mods), while the Loose Files version provides separate texture files for replacement via the textures folder.
Ahh, I remember now. Stupid me. I should've remembered all those ".bsa" files I've manually transferred to my Data folder!

Didn't realise you could have everything all lumped into one single file.
http://skyrim.nexusmods.com/mods/15052 is a lot better.
Heh, heh, waaay ahead of yah! Been using that mod for quite a while now, ever since I started Chadric's adventures. But I should note that those masks are retextures of the in-game masks,
not stand alones. They're bloody good retextures, but I believe Psychosteve's masks are all stand alones that you can craft and enchant yourself? That, in my opinion, makes them bloody good add-ons to the retextured Apophysis masks.

Just wish he'd hurry up and finish them off, that's all, 'cause it's been about a month since the last retextured mask. I know, you can't rush art, but I think a month on one mask is stretching things just a little.