Hey! I have to design the voice of a demonic snowman and this voice must sounds "icy"...
It may sound horrible, but try toying with using a reverb with an IR of glass or ice breaking/cracking.
You can also do a lot with breath. When I create special voices like these I spend a lot of time augmenting or even replacing the breaths and exhales of the actor with custom effects depending on the character and his mock-up, in your case you could use cold icy wind instead of the actor's breath, or cold whistles, crackling ice mixed in with it, etc. etc. etc.
I would also check out the movie "Thor" because I specifically remember the Ice God or whatever the bad guy was sounded really cool.
If you are having a voice actor perform the voice for you (which is a great idea, btw) make sure you get the best performance possible, with plenty of options. Once you have that in place and working, you may want to start layering in sounds of glass cracking or spiderwewbbing, ice cubes crushing, plastic twists, etc. Maybe those sounds can live under the consanants or percussive parts of speech. Maybe try more open sounds under the vowels, ie. Ice moans, glass rubs, crystal rubs, etc.
And see where that takes you!