They look pretty good. you may want to compress the texture size to better ease. also you may want to make the bum files just B/W jpg and let the users convert them. that way you can keep the zips of modest size. you may also want to think about leaving the bum files out of the mat files. just a couple things to think on. just keep in mind the easier it is to use your textures the more likley people will use your textures.