I'm thinking that to keep to weight down and to create volume around the body you are looking for that you could use various types of clear bottles and containers. Distort them with a heat gun and bind them together with a glue gun. I would use gloss clear & white spray paint to create a frosted effect at certain edges, depends how clear/opaque you want the effect to be. This technique would also allow you to work in layers. You could add some red in on the inside layers to depict frozen blood in the carcass. I suppose you could even add a layer off shrink plastic wrap to the outer shell to hide any imperfections.
First you could add some pale blue and pale lavender paint very thinly to give it that froze to death look.
Then you need frost/freezer burn!!! The super fine fake bagged snow that they sell for the-other-holiday is perfect. Or if you don't have any around, you can make your own. Hard white styrofoam - the sheets or balls or cones from the craft store type. Scrape with a knife to crumble or pulverize in an old food processor.
Spray glue in thin coats where you only want a dusting or hot glue where you want the crystals to look as if they've grown further. It will clump beautifully and any shine from the spray glue adds to the icy feel. Be sure to frost spots on the hook too.