There seems to be a new thing going around on Pixiv right now called ボカロ計画 or Vocalo-Keikaku (Vocaloid project or something). It consists of people drawing new vocaloid characters, basically.
The age-old question pops up again: is that a pool? Or a copyright tag (I would say copyright tag)? And do these images warrant a Vocaloid tag (I would say no)?
I've uploaded 2 designs by one guy, and put them together in a pool (pool #3382), but I think a tag is warranted for the concept (there are many more and they certainly need SOME kind of grouping).