First off, damn you for making an ice level on a game engine that's greasy enough as-is.
The level itself is decent enough. Besides the slippery controls the level is fun, and it does a good job of introducing and developing on gimmicks in the level, though some aspects (the vertically flying blue koopas for example) did drag a bit. I also think you might want to consider fixing where you place the rexes; a lot of them are on cliffs where they easily walk off of before the player reaches them.
The aesthetics are great, and have nice touches like the ? blocks with snow covering the tops of them. However, I think the music might be a bit unfitting. It sounds like an ice level, but it's too ambient. I would think a song similar to this
would fit the level better. That's just me, though, so you should probably see if other people think the song is fine.