This is great! I love the color palette, the story it tells, etc. One thing that stood out was the foreground character having no animation at all.



At bare minimum I would suggest making the reins hang down, they look frozen in the air as it is. If you were to animate one thing I would suggest animation the reins, is would be easy and go a long way.



If you animated a second thing, I would make the horses mane near his head flutter a little in the wind. One last thing could be to make the horses eye blink.



You may have intentionally left the fore character animated to convey a sense of frozen shock, Im not sure. If that's the case, I think it works.



either way it is a super awesome piece!