This was an interesting way to use "Frosted."
Nothing looked necessarily bad in this level. In fact, the NPCs' recoloring in this level is for the most part not that bad! I will say that the Spike Top and the fence BGOs, which are both a dark-ish red, don't fit in well at all with the general deep blue palette used in this level. The background also does look pretty good.
Some parts of this level are pretty good, but others fall short of decent, such as the P-Switch part, the Spike Top and unkillable jumping koopas part. Since this is also a short level, I would probably remove the midway point. If you'd insist on keeping it, I'd move it a little bit closer towards the end of the section, probably right before the Spike Tops. I thought the P-Switch part was a nice addition to the SMW styled level, but I would have either made the P-Switch run a little longer partially to make reaching the Blue Switch successfully a lot harder and because you can't grab the coins in direct way of the question blocks (the reason I'm penalizing that part is because it doesn't look intentional). I did think the grinder part was a smart-ish way to use them if they actually posed a threat. NPC placement also could have been a little bit less in waves and more spread out equally. I would also suggest putting in a lot more room in the main exit section.
This was kind of a forgetful level. Although the graphics are nice, it doesn't really flow too well as a level. The blocked jumping piranha plants & spike top area looks incredibly messy as does the p-switch tunnel and that reflected on how much I enjoyed it. I was at least able to move around, as it wasn't cramped or anything.
Nothing exactly special about the SMW overworld music, and it doesn't really fit well with this level either. I would have much preferred the SMW sky music, as I even switched from the overworld to sky music in the first section and I thought it fit significantly better. If you ever plan on changing around this level, I would suggest changing the music to be more fitting.
It wasn't a bad level, but it was forgettable.
Moved to Average
In an age of darkness light appears
And it wards away the ancient fears
March to the anthem of the heart
To a brand new day, a brand new start