The rules - at least from my vantage point - look to be pretty clear related to what tattoos mean in the workplace these days. My take:
1. Single Tattoos are no longer taboo - you have the cross, the barbed wire, a pacrim symbol for something, whatever. We've come to expect it and we're no longer shocked by it, and the numbers of people who will penalize you for that in the workplace are at an all-time low, and you probably don't want to work for the people who would penalize you for that. Exception is retail for the most part, and if you can cover up, who cares?
2. We only assign max creativity to people with large portions of their upper torso covered. This just in - we're yawning at the single tattoo as a indicator you're something different. When everyone has tattoos of some sort or another, they're no longer special and if you're not going to spice it up a bit, can actually mean something else. See #3 and #4 for trends related to upping the ante, or not...
3. No tattoos is starting to come back in style as "interesting" within some segments of the population. We've jumped the tipping point with tattoos where in some socio-economic and related strata where someone without tattoos is actually seen as fresh and interesting. It used to be that tattoos meant you were different and there was an interesting conversation there - now in some groups, especially young folks, it may be interesting if you don't have a tattoo because we've seen so many. What does no tattoos mean if you believe this? <Insert hiring bias here>. A lot of biases can be inserted. The point is that there are a lot of tattoos out there the younger you are and we've become bored with it.
4. Some single tattoos are seen as weak, meaning follower, etc. Seriously. You went with one tattoo and it's not that exceptional and it's small. Some people smell follower when they see that. You had to have one and you went single, small and average with the tat. Yawn. What about the kid without tattoos again? The younger you are, that approach seems riskier these days.
Those are the new rules of tattoos in the workplace. Special thanks to people like the Birdman (real name is Chris Anderson and he's pictured to the side) for lowering our sensitivity and making average tattoos normal and at times, average.