Those rocks look like they are sinking into the ground - like I said, your going to want to use doodads made for snowy terrain - those definitely aren't.
I generally don't like the sea weed doodad anyways, but if the waters freezing then there's no way sea weed would be growing (and it wouldn't be able to stick out of the water even on normal conditions - heck it can't even grow in climates that freeze like that).
I generally dislike the Ice waterfall doodad too, but I guess thats a manner of opinion.
Rocks do not grow over trees - so trees should not be sunken into rocks
Well its a WiP but the flat background in the second picture is bothering me.