very interesting topic by the way! congrats! well theres always 8 pieces( i think) so that would be of characters from 7-X2(hoping) if there was one:

Cloud(one of the most well known characters
Yuna (star in 2 games) plus Kingdom Hearts 2
Vivi (star kid that would be well known even if an adult
Squall (main character)
Rikku (known...first ff character to win an award!)
Tifa (just look @ her)
Red XIII (need a piece that looks different)
Tidus (first main character of a playstation 2 game)