top animation of the horse looks like a horse with a jockey. most of those guys are known to be short/small to minimize the weight to give them edge in the races. Like in many other sports, size matters here. so size is ok as far as i am concerned. Horse could be a bit longer though. Animation is definitely off though and could be done better. But even after saying that, i still think that animation in M&B for horses still a lot better then in most of the games i have played so far.
As for things i'd wish in the game:
ability to join with bandits (not khergits, but whole bandit group)
polished in-game ability to make your own banner. its already there, but it looks like it is unfinished and disabled (from reading thread about mod that enables it)
more ways to speed up footman based armies. maybe a wagon carts you can buy, a bit slower then all mounted army, but faster then foot army.
more options in sieges, as in control number of towers/ladders, ability to open gate by sneaking into the city, ability to destroy towers/ladders... (there are mods, but it really should be in native)
assassination is questionable, i agree here, but in old times, it was quite common for a fight between armies to be decided or preceded by fight between leaders. Why not to give us an option to duel against lord/leader of the war party. If he refuses/looses, his army loose moral and some soldiers will not join the fight for example.
more benefits of light armor. right now the only reason to use it is if you are god of fighting and want to handicap yourself. maybe add a skill to everyone that controls amount of protection and decreases encumbrance you get from armor like one for shield.
definitely agree on lack of options with prisoner interactions. raping and eating them is questionable (if they want to keep their game's rating), but exchanging with enemy lords for their prisoners as soldiers for your army, returning to the faction's leader for boost in faction's relation, giving them to lords to boost relationship with them...