I really want to go get a tattoo and I've been asking people about it, most say it is, few say its not, but I want to know why?
If it doesn't interfere with wudu and is not a picture of a living being and is safe, why do people say its haram? As I just wanted on my shoulder

It come from oral tradition, and is a matter of faith, you are subject to the rules of your local faith and the rules of the sect of Islam you practice. Islam like most religions are somewhat divided in beliefs esp when oral traditions are concerned.

But here is a good reason it is wrong.

Are Tattoos Allowed in Islam? Guidelines for Muslims (http://islam.about.com/od/islamsays/a/Tattoos-In-Islam.htm)

You should understand that religion is based on faith.