This is A LOT for a cc thread. Fewer next time?
1. I think you need either a longer or shorter shutter speed, to either blur the water smooth or to freeze it in action. At this speed it just looks fuzzy.
2. Doesnt interest me personally.
3. I think this would be a nice picture of the horse if you did some contrast in pp and maybe cropped the bottom a little bit, where the legs are in the snow. It looks weird where they just stop. The horse has a sweet expression.
4. Not very interesting, and maybe a little underexposed? Could be my monitor.
5. Same as 4, and seems a little out of focus.
6. blurry
7. Why is that horse so scrawny? Pretty scenery, though.
8. I like this.

Maybe either try to take out that dark corner on the top right though, or add a vignette so it doesnt show? It might also look nice with some contrast.
9. Odd angle, and the nose is blurry. Was it moving its nose?
10. This might be cute, but the top seems a little foggy or fuzzy and his ear is cut off.
11. out of focus
Why are the corners of some of your images dark? Do you have a lens hood that is in the way? In the horse pictures I like that, for the most part, you are down on the horses level or below it. That always makes animal pictures more interesting, in my opinion.
Edited to add - I see in your post that you said you dont know what the dark corners are. Sorry, missed that the first time! It is distracting, though...