In the harsh climate and rugged landscape of the great mountain capitol of Skyrim, one would expect to see great warriors on mammoths and noble white steeds, but how? Mammoths would be good for traversing tundras and plains, but not forests and mountains. Horses might not even survive the cold mountain climate unless they were specifically breed for it. Horses can get you through forests, tundras, and plains, but mountains? In Oblivion, horses were insanly good at climbing mountains, but im sure that it is going to be a bit harder in Skyrim. Of course, in a rugged landscape likethis, one would expect their mounts to die all the time. So what will happen with this? Will their be respawns at the stables so you never run out of horses and you can just keep buying them, or will there be another invincible mount like Shadowmere that you can earn? And about what horses will look like, not sure if anyone else has noticed this, but in this pic: http://preorderskyrim.wordpress.com/pictures/skyrim-trailer-windmill/ of a windmill, there seems to be a bay or chestnut standing in between the windmill and the cottage.

Frost Striders,

But seriously, I think that they should just have restocking horse vendors. Invincible horses just don't make sense unless it's some god in disguise

I agree, I don't really expect to see unicorns in Skyrim. All I want is like you said, restocking horse vendors, it would make sense, after all.