Giant Wolf?

What about a LOTR Wargh or some sort of chaos hound? You can bulk something up by using an armoured torso from a coldone or a horse or chaos steed and model a hound head and legs onto it, maybe.

Princess Mononoke!

http://www.toysnjoys.com/mononoke.html

Um, perhaps someone made some models to represent the giant wolves in the above film? Problem being of course, that they were anime wolves.

Here's a link. Not the best models, but maybe they can give you ideas. I like the elk better than the wolves here.

this depends on how much work you want to put into the mount.

but id take a jugernought of khorne and attack it with some serious filing then add a thin layer of gs to it and fur this up as for the head the dire wolf head works on this model as well, though you will have to model the neck a bit.

also whilst you are filing away have a look at actual pictues of wolfs so that you get the right look to his legs.

It's hard to tell but this half-dragon direwolf looks large enough to take a rider. Chop the wings and sculpt some fur and a saddle and you're go.
Maybe you could email them and ask how big it is? I don't think Dark Elves would let a little mutation get in the way of using a powerful mount

what about the mordheim 'thing in the woods'

http://store.us.games-workshop.com/...orignav=300816&ParentID=251918&GameNav=300808

if you've seen the film 'Brotherhood of the wolf' you too will think this is a very cool mini!