Hi ruffshod,
Firstly, good on you for organising a yearbook. Here are some ideas off some websites.
Name: (In case you forget in 10 years time)
Nickname: (Good fun teasing your friends)
Email Address or contact details: (For keeping in touch with)
Date of Birth: (Gifts later in the future)
Favourite music: (To be criticised and laughed at)
Greatest achievement: (Something that has completed you)
In 10 years time, I will be...: (Job goals/a fantastic island holiday/other)
Favourite memory of high school: (One you will always remember and treasure)
I will miss... (Can be a person/teacher/something else)
If I had to live in one moment of my life again, it would be.... (High school/growing up)
I will always remember... (Friend or a unforgettable moment)
Quote/Poem: (Preferably inspiration, said by someone famous or your own)
Farewell message to Year 12s: (Your final words)
and last but not least, their photo.
Let me know if I left out something.