Blizzard
is another, white white rose. I've only had it on once, as we usually go for Eskimo or Akito, but I remember it being a pretty white white.
I ususally explain to brides that very few flowers are true white - gardenias, stephanotis, freesia, hybrid lilies. Most other flowers and roses really are more ivory, some even greenish. Also, try using varigated greens with them - I think they look whiter when with a white-edged green like varigated pitt, or oregonia. Good luck!
tracy