The young white dragon from the Monster Vault is probably your best bet.
Like all white dragons, it has ice walk and it's the ice that is most likely to give it a homeground advantage. You could have a terrain effect making the ice have the following effects (this is just brainstorming: there's not a lot of thought behind these) on those without ice walk:
- moderate DC Acrobatics check or fall prone when you move 2 or more squares on your turn, are subjected to 2 or more squares of forced movement;
- when hit by a melee attack, moderate DC Athletics check or slide 2 squares and fall prone.
To tempt the PCs to move, you could rule that a PC that does not move 2 or more squares by the end of its turn gains vulnerable 5 cold until the end of its next turn (moderate DC Endurance check to ignore). After all, you always want to keep moving in a cold environment, right?
On a more positive note, you might allow a high DC Acrobatics check to do a sliding charge allowing the charging attacker to add +2 to its speed for the movement portion of the charge attack - but requiring a minimum of 4 squares of movement - and, on a hit, the attacker gains a +5 bonus to damage. However, on a miss the attacker falls prone. Or something like that. The point is, the ice should also be useful to a clever party with some good skill checks.
And, at the risk of trying to steal from a hack writer, there have to be icy stalactites that can be made to fall and impale a target. The dragon should be able to use these, as should the PCs.
BTW, in typing this reply I just realised how much fun an icy lair of a white dragon could be in 4E. I need to find a way to do this IMC.
Edit: I typed this before I saw [MENTION=6696971]Manbearcat[/MENTION]'s response. Sorry for any overlap in ideas. (And I'm going to steal some of his.

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