We're going skiing in a couple of weeks and taking our DD, who is nearly 16 months old.
A friend has lent us a one-piece snow suit, and I'm going to hire some proper snow boots (aka apres boots) for her. We will also buy some mittens and a good polarfleece hat (thought I had one, but it doesn't fit anymore!). Sharles' idea of the hat that ties underneath the chin is good, and with the mittens I'm going to tie them together with a very long shoelace and thread them through the sleeves of her suit IYKWIM.
DD is going to creche while we ski, but we want to take her to play in the snow too. I don't know where you're planning to go but if you want to put her in the creche I'd book now as they fill up fast. It's expensive though at $87 per day (Perisher) but that's skiing for you!
I also worry that with a backpack I'd fall over with her in it so I think we'll skip that. If you're planning on snowshoeing you could possibly try dragging your DD along in a toboggan or sled?
I can't wait, I am hanging out for some skiing... and this year I won't have to ski back to the creche to breastfeed her. Woohoo!