For 10 of them, you need to collect a certain amount of NP total (usually at 10000 point intervals, but the last requires 99999 points total). For the 11th, you have to input a password. Both of these tasks are done by going to "Tree of Guts" mode (in between story and wireless modes, I think). --- "No matter how far a jackass travels, it won't come back a horse." Batou; Ghost in the Shell 2: Innocence
Sorry, between online and option modes. And the password for the wallpaper is Fire-Ox-Rabbit-Horse.
For those who are unfamiliar with the password screen, the symbols are like this.
1st screen (input 1 character) Fire - Wind - Lightning - Earth - Water
2nd screen (input 3 characters) Rat - Ox - Tiger - Rabbit - Dragon - Snake Horse - Sheep - Monkey - Rooster - Dog - Pig --- "No matter how far a jackass travels, it won't come back a horse." Batou; Ghost in the Shell 2: Innocence