A while ago I had an idea for a megadungeon that was carved into a giant glacier or ice shelf, dozens of miles thick. As well as the normal inhabitants of a dungeon, PCs would have to deal with the brutal cold and environmental hazards such as collapses and so forth. I'm fairly sure I discussed it on this episode of A Gaming Podcast About Nothing; but in any event it's what I want to run when Patrick finally finishes The Veins of the Earth, using his cave system rules for icy ones.
Apropos of that, here is an incomplete list of glacier dungeon inhabitants. These are things that are either explicitly arctic/mountain/ice based, or logically should be so. (Monsters like crab-men should definitely be there: some of the biggest crabs in the world are found in the Arctic Ocean.)
Straight from the 2nd edition Monstrous Manual
Beholder and relatives
Selkie (in glacial lakes)
Non-existent at this time but formed by putting the word 'ice' in front of a Monstrous Manual creature
Ice werebear (were polar bear)
Ice merrow (in glacial lakes)
Straight from the Planescape Monstrous Compendia
Since, as any fule know, hell is a place of cold and ice, in the lower regions of the great ice glacier there will also be encountered demons and devils, who slip in from the Abyss or the Nine Hells. Also, magical constructs and undead can also make appearances.