Still, would we want to implicate "original" to this or not? Or, do we want to manually tag original on pixiv_fantasia pictures that contain original character designs, but not on pictures where someone else redrew that design?
I'm in favor of the latter, because to me it seems like kind of a parallel to something like pixiv-tan, where you can have both the copyright (since that's the basis) and the original tag (since practically all of them are original designs).
Basically, I think people who are looking for original will want to find those pixiv_fantasia pictures, and it also gives accurate information as to what's contained in those pictures.