Mine is my name that I use for just about everything online. I chose it because it's floral, lovely, and rarely taken. I like consistency too. It's rather hilarious listening to people try to pronounce it. I like "Lili-ya", but a friend of mine says it "Lilzsha" soft on the zsh sound, and that struck me as very pretty and graceful. It's such a common ID for me, I have RL friends that I met online 9-10 years ago, that still call me Lili. It's close enough to my given name, Lisa, that it works
My avatar picture is Arachne though, and that's another name I take often. I've considered changing it here, too, just to make it match the picture, and the whole web spinning, everything's connected, weaving a story nature of the cards.
Edit: good question, too, very interesting to read people's "why"