I'm thinking of mass tagging characters with letters (as well as foreign ones) to possess a letter_head tag.
Characters I'm aware of with letter-shaped heads-
t-head_admiral 2.2k posts
p-head_producer 1.9k posts
t-head_trainer 725 posts
s-head_commander 129 posts
u-head_trainer 26 posts
c-head_commander 10 posts
s-head_sensei 7 posts
sa-head_saniwa_(touken_ranbu) 4 posts
d-head_doctor 3 posts
p-head_producer_(cosplay) 1 post
Combined, make for 5634 posts.