In the first post at
http://www.minecraft...e/page__st__440 you can find the terrain.png of a very early version of the pack with things like a cabinet instead of a bookshelf, light wood, diamond and lapis lazuli block alts, and maybe a couple of other things I'm not noticing.
It does have some Gerudoku blocks stuck in there also (mushrooms, sapling, reeds, cactus, crops, pumpkins, cake, bed, spiderweb, maybe a couple others), so watch out for that if you do decide to add some of the textures in there to the customizer.
Anyway, I wish you the best of luck with this project. If it comes through with the promise it shows thus far, it will make me very happy.
EDIT: @Duru: The textures you've shown so far, especially for the BTW mod, look fantastic. Nice job!