I have many tattoos, covering all of my body, and have even had my gall-bladder and liver tattooed in case I get in a car accident and my insides become my outsides, in which case I would want my insides to look as 'cool' as my outsides. If you don't know if I look cool or not, check out my photo. I am very cool.
To have your eyes tattooed as eye-liner is a very good idea. You should also have your retina tattooed so when your partner looks deep into your eyes they will see a little message there like "I love you" or something.
O yes. Tattoo everything. That's my advice. Don't stop until you look not like a human being, but like a walking tattoo. And then tattoo the tattoos.