I think I am more likely to go with a stencil since that might look more imbeded in the skin. What you have here looks pretty go though still a bit stick-on. I wonder how it would be possible to get more of the skin variaton added to the tattoo so there appeared to be skin over it? In photoshop there is the buisness of soft light and hard light which give the feeling of either being blended under or over the base... both do unwanted color shifts though. I wonder if a crude simulation of skin over the tatto could be obtained by blending a granite node with the stencil before blending it to the skin... noise like that can fool the eye even if it is not a true match to the surrounding area. Maybe some sort of edge blender on the tattoo before it is blended to the skin... would that make any sense? The ink would look deeper under the skin on the oblique angle?  But if this is to be something I can do it must not be too complicated... I have unreasonable trouble understanding Poser math nodes. Thank you for your interest.