Tradition: Whips, Wax, Chains, Bites, etc
One of the stereotypes is evil, violent Reds - consider how many in the earlier book end up being Black Ajah!
To play with that, some Reds joke around about whipping, waxing, biting, chaining, etc and use pictures of those type things in their sigs. It's a way of mocking the stereotype. Some Reds don't feel comfortable with this and don't do it. Whether or not a Red does this is completely up to her.