There is no "best pet" for any school. What matters is the pet's talents, and you won't get a perfect combination of talents in a first generation pet, so you'll have to hatch with other pets that have the talents you want.
The Guardian Foo Dog can be a very nice Ice pet provided it manifests some of it's better potential talents. With mine I was lucky enough to get may-cast Freeze, Spritely, Blade of Ice (gives Ice Blade card) and Snow Born which adds a 100% accuracy Blizzard card to your deck.
The snowball pet is kind of fun. It gives a unique ice area of effect damage spell "snowball fight." It seems to give more sbf cards as it levels up, at least I have one that currently gives 2.
I think you can buy the snowball during december or january in the crown shop.
The biggest problem I had was waiting until level 38 for an ice blade. So buy Hoard of Hydra packs until you get Snow Beast or wait until December when they release yuletide packs for the rescue rover. Those are the pets I recommend until ice wyvern and Lord of winter.