1st, do not take a picture of a tattoo that belongs to someone else and steal it by getting it tattooed on you also. Bad form.
You can however take a picture of a tattoo, a real image, a drawing, an actual object/thing, written descriptions, etc. and you can take a combination of all of these.
You tell your artist what you were thinking, you say: 'I like this part of this picture', 'I like this style', I want something like this, but smaller/larger/and with this and that', 'I want these colors', etc. etc.
Your artist will then work with you to draw up a custom design for your approval. When you are happy with the image, and the tattoo artist and you are on the same page about it, and you have asked every question to satisfaction, then you set up an appointment or start right then to get tattooed. Your artist will know what works and what does not for a tattoo to stand up well over time. He/she will also take into account your anatomy and placement and size. He/she will tell you how much it will cost, and about how many sessions (and about touch ups). You will agree and sign papers to that effect.
You should tip 15% - 20% also.
You should do excellent aftercare for your tattoo to heal properly and for your image to look it's best when it has healed. If you need a touch up you do it then, and start the aftercare all over again (2 - 4 weeks).
Here is an excellent info. site:
http://tattoo.about.com/
good luck