Most people turn to Google images to start finding artwork ideas for their new ink. I don't think this is a good idea, and the reason is is because everyone else is doing it. It means you run the possible risk of duplicating someone else's artwork. Not good!
What I would do if I were you is look into a pay tattoo site. I think that these sites offer numerous advantages over looking for free artwork. Such as? How about having access to a tattoo artist that specializes in only tribal ink. You can also gain access to a huge community of like-minded tattoo lovers that can help you out with any questions or concerns that you may have. Most of the best sites also offer reviews on local tattoo parlors so that you don't have to worry about finding a shop that is clean, safe, and reputable. This alone can take away a lot of your worry.
So make sure that you do good research so you're happy with your new artwork. Good luck on getting your new tribal lizard tattoo!