On the off chance that you, too, want a screen name from Hamlet that will confuse people:
Squeak & Gibber
Cursed Hebenon
Puff’d and Reckless Libertine
Honest Ghost
Hyrcanian Beast
John-a-dreams
Murder of Gonzago
Very Like a Whale
Soul of Nero
My Lady Worm
Infinite Jest
Eat a Crocodile?
This is why I love Shakespeare…
I am growing rather fond of the names in the book I am currently reading.
Ria of the Marii
Caecilia Metella Dalmatica
Livia of the Drusi
Servilia Caepionis
Aurelia
Clitumna from Unbria
Nice roman names. 
Maybe I should just choose a Greco-Roman type name. They’re so poetic…
Hmm. It would be nice if I had read enough Shakesperean plays…
Jester liked the idea of me being FenchurchIV. From Douglas Adams…I would like to be known as the girl having sex with Arthur.
How many letters can you have for this new name, oh Isis AstarteDianaHecateDemeterKaliInana
Well, there is an Arthur around the boards somewhere.
Or you could be Granny Weatherwax, or Gytha Ogg. (Yes, I know, not Douglas Adams.)
Actually, I like DireWolf’s idea of “Elvira, Mistress of Spuds,”
or your could be PotatoZog
"I am thy father’s spirit,
Doom’d for a certain term to walk the night,
And for the day confined to fast in fires,
Till the foul crimes done in my days of nature
Are burnt and purged away. But that I am forbid
To tell the secrets of my prison-house,
I could a tale unfold whose lightest word
Would harrow up thy soul, freeze thy young blood,
Make thy two eyes, like stars, start from their spheres,
Thy knotted and combined locks to part
And each particular hair to stand on end,
Like quills upon the fretful porpentine:
But this eternal blazon must not be
To ears of flesh and blood. List, list, O, list!
–Hamlet, Act 1, Scene V (emphasis added)
I can only make it 15 letters long so Elvira is out, I’m afraid.
I’m still pondering. (I’m way too anal rententive about this all. Sigh…)
Zorba the Geek.
I’m not a geek! …not…really that is. I always thought I was just a step away from James Dean, and definitely cooler than those kids in The Breakfast Club. Pssh. Me a geek. Whatever gave you that idea? 
reanimated
ash
drillerkiller
virgin sacrifice
redrum
sucubus
christopher walken
Madeline Albright
ummm
bloody mary?
The scariest female name I’ve ever heard: Schlessinger
Okay, okay… Baby Blue Cthulu?
BTW, I really like the name Zoggy, don’t know why.
Koala Tea of Mercy
(It’s from a long a boring joke; basically, the tea, in this small Austrialian town of Mercy, is very lumpy, and perhaps some of the lumps are still alive and squeak most pitifully. The reason why the tea is full of lumps is that the Koala tea of Mercy is not strained.)
I’ll just go off and hide in a corner now, shall I?
There is a recent thread, here, that you minght find helpful.
RoBooty3000. Or the more suggestive RoboBooty3000.
Or not at all.
I’m leaning towards FenchurchIV, though if I could find something strange and obscure…maybe I’d go with it.
Slartibartfast?
that one ain’t so bad neither. Would be nice to be known as the guy who created Norway.
Or…how about FortyTwo. The choices are endless.
How about Zoinks!? or perhaps just sticking with your nick as it is?
punk snot dead,
broccoli!
Well, I was going to suggest you just go with Purple Soup. It has a nice ring to it if you ask me. It also kind of sounds like a band name.
Of course, if it weren’t for the silly 15-letter rule, you know that I am always trying to get someone to take “Chicken of Bristol” off my hands. It has been rejected twice already by people looking for new names so I’m used to the rejection!
However, I really like Bumbazine’s suggestion of Baby Blue Cthulu! It’s way cool!
I don’t have a suggestino, I just popped in to see if evilbeth tried to offer Chicken of Bristol agian.
So evilbeth, did you offer Chicken to me originally, or had it already been rejected once by the time you got around to handing it my way. It’d break my heart ot think you’d offer me a hand-me-down user name. 
Actually, Crunchy, you were the very first person I tried to unload the Chicken name on. Feel honored! Agisofia (now Thea Logica) was the second)
However, I won’t be counting this one as a rejection since it does not fit the prerequisite for length!