It is more than likely that you have already gone to Google images to find artwork. The problem with this is that so has everyone else. You are getting a tattoo because you want something unique and you want to stand out. Using artwork that is freely available online is a bad idea.
I would recommend that you check out a tattoo gallery that you have to pay for. The benefits of this are being able to find an artist that specializes in tribal tattoos. With a pay site you can find an artist that will work hand-in-hand with you on your new design. You will also find better quality tattoo galleries than free websites. And you will find a community of like-minded tribal tattoo enthusiasts that will gladly help you out with any questions that you may have.
The other benefit is having access to an updated list of local tattoo galleries. You can find reviews and recommendations of trusted tattoo artists. This alone can save you a lot of headache.
As you can see you have a lot of decisions to make before you get inked. I want to make sure that you find the right tribal turtle tattoo artwork that will make you happy.