Ok, let's see..... perhaps the Nether Salts could be a greenish gray-white, just to set them apart (sort of like a whitish version of the ectoplasm. Yes, looking like a salt, grainy. If you find something which looks totally Nether Salts, use it and I am positive I will be happy with it. I trust your judgement, use my choice as a guideline.
Or if you think it would look cooler. I would also like a dark texture (close to black but not pitch black) with spotches of ectoplasm green in it, still in the form of a grainy salt.
Hmmm... okay, http://i468.photobucket.com/albums/rr50/Alaisiagae/Mod%20Screenshot%20MW/Misc/nether_salts_v1.jpg?

Just an initial attempt, so if it doesn't fit the bill, I can try some other things.