>>49582372
Maybe it has to do with the practice of nailing dolls to trees. The album is called "Hourai Dolls" so you would assume the girl on the jacket is supposed to be a "doll", even though she's not made of straws. There is also an example of that ritual in the album.
Alternatively, considering she is holding a cross in her hand, it could even be alluding to the crucifixion of Christ.
Lastly, it looks funny.