Everything on his soundtrack is depressing. Except two songs.

Missing - Evanescence (Lyrics cited on card)
It was thanks to a .hack//SIGN AMV on Youtube that I even discovered this song. It definitely fits Tsukasa because his father doesn't care about him.

Imaginary - Evanescence
Tsukasa uses The World as an escape from a "ludicrous" reality.

Nobody's Home - Avril Lavigne
Tsukasa's problems in real life have broken him on the inside.

Wired life - Meisa Kuroki (I looked and looked, but the original full version by Meisa Kuroki isn't on YouTube.)
Tsukasa can't escape from "The World", and at first he doesn't mind.

Forgotten - Linkin Park
Tsukasa's always lingering on his memories.

By Myself - Linkin Park
Tsukasa doesn't trust people and tends to isolate himself.

Drive - Incubus
Throughout the series, Tsukasa is manipulated through his fears. In the end, he decides to face them.

Program Used:
Photoshop CS5

Image Credits:
grunge texture -- designtreasure.com
hexagon pattern -- Google images
Tsukasa -- (c)respective owners

Fonts:
Consolas