A naughty idea an ex gf had was a tat of a rabbit on one of her cheeks looking like it was running into her crack. Wearing underwear that her mother would be proud of on a young girl you wouldn't see anything at all, but with
nickers that showed some cheek you'd see a bunny tail and a couple of rear bunny legs and nothing much else, and with a gstring you'd see most of the body of the rabbit as well, and it would need someone really intimate to see the rabbit's front legs and see where it was going. I found that tatoo to be a very sexy idea. Subtle but sexy.