User blog comment:BMHKain/SEASON III Fights (Plus Hints for 30 Characters for SEASON IV)/@comment-25656629-20150913005529/@comment-25656629-20150913151155

Hmmm..more guessing:

Utsuho Reiuji (Hopefully I'm typing that in correctly >.< and assuming her being a Background Character in HM also qualifies)

..and my inexperience with the majority of Touhou is showing, I really should know the Green Magic one..

As for #17 it seems to either be Homura or Mami. And I'm gonna go with the former

And for #14 I want to say Akari, but I have a feeling that's incorrect.