1) An awkward picture from middle school or early high school. The picture should epitomize the unfortunate years we all go through around age 13-16, the years when your pimples outnumber your friends.
2) A picture of how you look now, one that shows you at your best. You know, like your last Facebook profile picture.
I think it will provide inspiration to 14 year olds everywhere to see that the terrors of puberty don't last forever. If anything it should be interesting and pretty funny.
Oh yeah. Email me at firstname.lastname@example.org. Thanks!