What other animal followers/pets could there be? Other than dogs, cats of some sort and maybe falcons? Maybe the toughest combat animal could be a timber wolf/dog hybrid? It's hard to come up with animals that would make sence and would have a purpose as a pet when it comes to combat and exploring. there could ofcourse be new type of animals, but Beth seems to want Skyrim to be as realistic as possible, so no flying man-bear-pigs any time soon.
I would love to see a Senche Companion. For those who don't know, the Senche are Khajiit born under a certain moon phase. They are large, burly and can be ridden like horses. But they are not mere pack animals. They are fully sentient Khajiit. In The Infernal City, they able to leap onto ledges and large branches, even with someone on their back. They can sprint for short bursts (which, even on the page, sounded like a game mechanic) and be of all, they talk. They think. A Senche Companion who joins you, just as Boone or Fawkes, would be someone to get to know. Someone who hates carrying you around on his back and gets in hissing arguments with you now and then. The juxtoposition of having a mountable, packable creature, who you also have to respect as a peer is a facinating one and could make for a interesting relationship.
Beyond that, what about poison snakes for assassins. By "equiping" it in one of you hands, you see it coil out of your sleeve into your palm and then by pointing it an an enemy, it would slither off and bite them.