Generally I understand that scars won't take the ink as well as normal skin. (I have a scar on the arm where my sleeve is. Unfortunately for me it's also where I have a huge patch of black and you can see quite a difference.)

A really good artist can usually make up a design that can distract or incorporate the scars though.

I dunno if this link will work but if you go to google images and type in tattoo covering scars or something you will find a lot of images.

https://www.google.com.au/search?hl=...too+cover+scar