Respectfully, neither of those photos show Trayvon's face and there's no guarantee that they're Trayvon Martin's tattoos. I believe the one that says "Sybrina" is likely his, because that's his mother's name, but I've never seen a photo of Trayvon that shows his inner wrist, and that tattoo is clearly on an inner wrist. Therefore, we can assume that it's Trayvon Martin's tattoo, but we don't know that for certain.
As for the other, large, tattoo, I don't know that it's Trayvon's. It's on a right upper arm and says "Nana." I don't see that tattoo in the photo I posted above of a shirtless Trayvon. He clearly appears to have a tatto on his left upper arm, but you can't see a tattoo on his right upper arm.
Remember that Trayvon Martin posted photos of other people on his MySpace page - he's posted photos of two rappers that people have mistaken for him. Until we have a photo that shows his face and his upper arm with that tattoo, it's only an assumption that the large tattoo he posted a photo of his tattoo.
The thread about Trayvon Martin’s second twitter has a photo of Martin with the dartboard in the background and his upper arm is visible with a tattoo on it. Comment 7.
http://www.freerepublic.com/focus/f-news/2866397/posts
Sheesh, I saw your comment before looking up the thread, you posted it right up above my comment!
I should read more and post less....