Really atmospheric level. You used two SMW themes/tilesets to do a really good job. Very well designed and planned, this have some hard parts too. It's not a problem, but some parts can give so much work to the player. I liked the use of Bullet Bill Launchers. Three different types: The normal one, other who replace the Bowser Statue and other who shots a jet of flame (like the Dinos in SMW). The best part (and the most hard too) it's the moving lava cavern. About the music: It's good, but don't match very well with the theme. It's not a major problem. Even if you don't have big new gimmicks, it's a very well architected level, with good atmosphere and very well planned. I suggest you to decrease (just a little) the difficulty of some section parts.
Design - 4/5
Amazing idea; Not so well executed in design. And this have some hard parts because of the design too. Like the moving lava cavern section (after the checkpoint). I liked the gimmick, but you can't walk speedy and have to pay caution to a suddenly fire/torch. In the another section, so, it's difficulty too, because you have to wait a little to do a speedy movement. But that's not a major problem. I think you just have to make some parts easier than now.
Placement - 4.2/5
Some places don't have any enemies/NPCs; In the other, you can see a lot of them (counting with the jet of fire). It's strange. Because you don't know what will happen if you do a long jump or whatever like this. Remove some of them or do any modification in the placement.
Atmosphere - 4.7/5
The mix of tilesets provided a beautiful atmosphere (even with the music not helping very much). The different Bullet Bill Launchers brought something nice (although not the first time I saw this idea). Anyway, if you change the music, in this case, the atmosphere can be better. Anyway, all the placement of spikes/plants give to a beautiful thing too. The mix of tilesets, like I have said. And the backgrounds matches with the cavern and the castle blocks (if you made a mix with this backgrounds, however, would be much better).
Aesthetics - 4.6/5
It's fine, but with some improvements in the other things (design/placement), can be better. Some parts can be improved with a better design and placement. With more BGO objects. With some changes in difficult (in some parts). But I liked the way you have made this level (however, the very challenging parts is a major problem;
Overall - 17,5/20 or 8,75/10