First, I'd rub some cool minty lotion on it, to get flesh soft and nerves tingly. Usually, I'd start with navel finger wiggles, but your piercings would be there, so I would begin with light fingertip feather strokes under the navel, back and forth, catching the hips on the far ends. When the lotion dries, I'd nibble and suck the flesh around the navel area for awhile, then nibble your hips until you went bat-shit nuts.
Well, I would tickle it slowly, certainly play with the tattoo abit... But really use it as an excuse to initiate tickling so I could eventually make my way to your feet