Sweet God! Look at all that people! This picture is focused on characters from different high school anime (and manga) series. So we have some of the cast from: The Melancholy of Haruhi Suzumiya, School Rumble, Cromartie High School, Azumanga Daioh, ToHeart2 and Pani Poni Dash! Here's a list with the characters that I included along with their respective universe (must of them should be pretty obvious for anyone who already saw or know about them.

Azumanga Daioh: Chiyo (flying girl with pigtails), Osaka (girl coming out from the right), Sakaki (serious looking black haired girl) and Kamineko (grey cat).

School Rumble: Tenma (long black haired girl with the small pigtails), Harima (guy with shades and goatee) and Karasuma (oblivious looking guy with short hair).

Cromartie High School: Kamiyama (guy in the bottom left), Hayashida (guy with the purple mohawk), Mechazawa (the robot) and Freddie (guy with the moustache)

Pani Poni Dash!: Becky (blonde-pink haired little girl), Himeko (the other flying girl that says "Maho"), Ichijou (brown haired girl with the weird eyes), Surizawa (blue haired girl with the nekomimi hears) and Mesousa (white rabbit).

The Melancholy of Haruhi Suzumiya: Haruhi (brown haired girl with the yellow ribbons), Mikuru (girl next to Surizawa), Kyon (guy with the red tie) and Tsuruya (long-green haird girl that likes to LOL)

ToHeart2: Karin (blonde girl with the pigtails and pink uniform)

This picture took a lot of time and patience, but at least it came out nice, IMO. Hope you all like it!