This disorder is associated with several vascular, neurological, and skeletal problems including stroke, heart attack, clotting, mental retardation, eye abnormalities, and osteoporosis, amongst many other complications.
Tattoo tipping etiquette, in general, should hover around 15% for small tattoos and 20% for larger tattoos, but as with all tips, you as a customer ultimately determine the amount based on the quality of service and the work performed. Consider your involvement as well.
*tries to get a $1000 dollar tattoo with $300*. Not too bad, but not actually the most clever cover up there is. Your tribe will be very, very disappointed. This one's probably drawn on with marker too, but man, it's just wrong. A classic cover up.