I can't share a picture here, but I chose a modified I Ching (yin and yang). Instead of having the two colors side by side I had the black put on top to symbolize black/white, Master/slave, man/woman. The two sides slightly bled into each other to show how the two were becoming one, that there was no clear cut separation.
Can't post pics on the boards. It's not allowed. Best anyone can do is a link to it short of sending it privately. I don't have a bdsm symbol type tattoo, but do have one that was the result of a very important lesson learned from a dominant who remains a good friend still.