Zell was drawn with the "main character of a shonen-manga" image. Beforehand, Nomura saw a music clip on MTV featuring a man with an all-over body tattoo. Remembering how cool it looked, he decided to add a large tattoo on Zell's face
Source - FLAREgamer | Tetsuya Nomura's 20s

At the bottom of the page, it shows:

Sources:
Squaresoft Staff
Ultimania & Dismantling
V-Jump & Famitsu
I really don't know if this information is reliable, but who knows really. Noruma did not mention Adel or Ultimecia tattoos . . .