As Ascension said, it depends what you want to convey. My first thought from your handle was an eclipse, but equally you could use thunderclouds or a Ringwraith, or...

...and it doesn't even have to be about your name.

I doubt if you'll get much of any use from us unless you give us a clue about your preferences - there are too many possibilities.

You're the best person to devise something you like.