I don't think anyone will have a problem with this, given that Knytt Stories is freeware. If you'd charge money for this, then that would be a different story of course.
We have a big level torrent too with many levels. You could consider using that. But a package that is ready out of the box is nice too. Of course, the official download does come with a few levels, but more levels is always nicer.
I do think that such package should include a small textfile saying that this is all free, and that if you paid for it, you should get your money back, and also that you cannot share this if you ask money for it, because it is still copyright protected property.
So if Nifflas gives his approval, which I think he will, then add that to the textfile too, including the link to where you can download it seperately.