The material component aspect of using magic in D&D is something I have never really seen imposed with much rigor. From my experience, a bit like auditing encumbrance and book keeping in general, its not really very interesting, narratively irrelevant and can keep tripping the flow of game - it brings no enjoyment. There have been a number of articles over the years trying to refresh these perspectives and suggesting methods of integrating these mechanics into more relevant and exciting gameplay but to be honest, I have never really bought it.
Sporting over 100 tattoes to decorate your particular species of choice I also find it engaging to browse through as if I was picking out something for myself. DnD has always been somewhat bitty as it has evolved from a lot of different versions and realms so whilst there have been some great examples of artwork it has never been that consistent compared to something like the Warhmmer universe for example. But encapsulating a visual theme into a sourcebook is an interesting way of painting a GMs world where the skin itself is the canvas. There are also mechanical implications as for example vocal spells can be inscribed on the throat area, fighting spells on the arms, agility on the legs etc etc More so it potentially raises a rather uncomfortably economy if indeed the skin can be removed and still retain the magic inscribed upon it. Seems that tattoo art can go down the generations, literally.