My username's origin isn't terribly interesting. Back around 1995 or so, a friend of mine was running a D&D 2e game, and he had created a highly variant magic system he wanted someone to try, and I borrowed the character name.
My avatar has a bit more story behind it. It goes way back to the early days of EN World, before I was a moderator, and possibly back when Eric Noah ran the place. The original image was lost in the Xenforo upgrade, unfortunately, so I replaced it with another picture of the same character.
Back in that time, I didn't use an avatar. And the moderators were a raucous bunch. They goofed around giving each other avatars as jokes. One of them (I think it was Darkness) decided that I, just a user, should have an avatar that spoke to my posting habits at the time...
The picture is of Lindsay McDonald, an evil lawyer character played by Christian Kane on the TV show Angel, which was current at the time.