Quote - For areas of the back, I'd recommend that one work with V2/M2 textures, and then UTC them to V3 or M3 if that is the figure desired.  That way, one advoides haveing to split a tattoo image in half and then trying to match up seams.

I apply my tattoos in layers, usually three.  The first layer is usually a burn color layer, over which a I apply an Overlay layer, followed by a Normal layer, but set at between 50%-85% opacity.

What is the purpose of the burn color layer? Does it matter if you are using just a black tatoo? I've always used a normal layer at about 50% opacity over the tatoos. (Actually, sometimes I use an additional selection at a higher opacity -- the opacity which works for one tatoo doesn't always work for another.

One hint that I will make is that if the original skin doesn't come with a bump map, use the original for a bmp map rather than the tatooed version. (Same goes for eye makeup.) I have an otherwise very nice render where it looks like the character troweled on the mascara ...

As a side note, I also paint miniature figures, and I usually do tatoos on them with a fine felt-tip, and then paint over with the base skin tone mixed with clear (Future Floor Acrylic) to get the same effect of the tatoo being in the skin.