I know this is going to sound peculiar, but I don’t actually picture the person (apart from Anal Scurvy, I have quite a clear image of him for some reason), I picture their computer on their desk.
I’m not going to describe all the different images of sleek laptops and ancient grime encrusted workstations in my head; I really don’t want my fantasies ruined.
Yookeroo reminds me of a kangaroo hopping around in the American Midwest.
All right. This is longish. Genders are probably wrong as I picture most people as men.
Smeghead is yes, a large penis. sorry
Eats_Crayons… I picture an average collegiate man sitting at one of those little kiddy tables from kindergarten slowly eating crayon after crayon.
Qadgop the Mercotan A cartoon owl doctor. (I’ve been spelling your name wrong every time I mention you. I hereby apologize)
Shodan Hiro Protagonist from Snow Crash. Swords, computers, motorcycle.
Sanguine Spider A scarlet female black widow. Very pretty.
Ilsa_Lund a man in Greta Garbo drag.
DeagontheWolf You are Rutger Hauer from LadyHawke.
Guinastasia I actually picture the little pixelated princesses from the end of each level of Wizards and Warriors from the 8 bit nintendo.
Siege Ardred drew up a D&D character named Siege that was a dwarven fighter with spikes completely covering his armor. He liked to hug his friends without realizing he was killing them. That’s what I see.
jarbabyjI see the shelves and shelves of fetuses in jars in formaldehyde.
dangermom Dangermouse in an apron, holding a rolling pin and wearing glasses with a beaded string around her neck to hold them on.
polycarp is a large catfish of many colors wearing glasses.
Coldfire demon of blue flame with a lightning bolt scepter and a smoldering computer
Scylla is one of the crabs from Finding Nemo. HEY. HEY.
Greenback I see a large gorilla with green rather than silverback hairs.
Tomndebb I always picture a young couple sitting together around the computer and posting by candlelight.
I’ll ask. What about me?
Guinastasia – a South American Revolutionary. Fatigues, bandana, machine gun.
Phlosphr --an old man in a robe, bald, whit haired, long white beard. Not unlike the old wizard Shazam, from Captain Marvel.
siege —the toy plastic catapult I had when I was a kid. It was a siege machine.
Ya’ll are much more creative than I am. I don’t see any images from Dopers’ usernames.
(Now do me).
Shplebordnick reminds me of a sound effect from a Mad magazine cartoon…
** The Great Zamboni** --Circus Ringmaster/carnival barker/traveling medicine show huckster. Waxed mustache, curled at the ends, top hat, red jacket, etc.
Scylla – a bit monster from one of the less well-made Godzilla films. Giant green serpent, multiple heads.
But makes lovely brownies! And fudge! You could die for Scylla’s fudge!
FilmGeek - is a touristy type, wearing a camera around his neck and khaki shorts and roller skates.
**monstro ** - looks like Mr. Clean and goes to monster truck rallies wearing a wifebeater and a big gold watch.
**The Great Zamboni ** - travels around on a zamboni and delivers pizzas (when I read zamboni, I think of pepperoni)
And **Chicago Faucet ** makes me think of a guy in Chicago with a huge penis (I think this goes back to my first time on the internet when I was thirteen. My dad was standing behind me, and I entered a chat room and saw there was someone there named The Big Faucet. I remarked, “I wonder what that means. Do you think he’s a plumber?” And my dad said “Umm, yeah, or maybe it has something to do with a certain sex organ.”
Grasshopper- Scientist looking guy complete with glasses, and an odd looking body. the man looks like a walking bean!..or grasshopper without the limbs.
FilmGeek- You look better than you would lead others to believe. I think of Dawson (from Dawsons Creek) when I think about your name.
Chicago Faucet- Big fat italian plumber. From Chicago of course.
Ooooh ooh! Do me! Do me!
Machine gun? Please. I’ll leave you alive, but only if you’re female. Schoolgirl uniform a plus. And in any case, you’ll be too preoccupied to bother counting tentacles.
H. P. Lovecraft… I tried to read some of his stuff, but I can’t dig his writing style.
Stephen King: I’ve read It, The Stand, Rose Madder, the Bachman short stories, Needful Things, and a copy of The Shining that, for some reason, had most of the dirty words censored out in black magic marker. The word “shit” was left in, but many instances of the word “pants” were marked out. (Hold it at the correct angle, and often you can tell what the word is.)
Call of Cthulhu: Nope. I don’t play any tabletop RPGs with any regularity. I’ve never even been in any campaign.
True, you betcha, and if by “show” you mean “movie”, right on.
Bosda Di’Chi of Tricor doesn’t give me anything visual, but reminds me of Boston and Tricorder.
Greenback is a large green frog. 
mangeorge is orange!
ANd Coldfire is ice blue…
Hmmm… looks like a little bit of synesthesia here.
That sounds like a good practical joke I could pull, kind of like something from The Jamie Kennedy Experiment.
I wish I could be that good of a showman. I must look fun to you.
Grasshopper does not remind me of an insect, but of a guy that thinks he is a master of marshal arts, even though he can’t even throw a punch.
Bosda Di’Chi of Tricor reminds me of a lord of the rings character that Mel Brooks or Monty Python created (Yes, I do know that Monty Python is a troupe).
I’ll try a few more…
The Great Zamboni dresses as a stage magician while riding his ice machine. The waxed mustache, etc…
Tentacle Monster has a huge basement room full of racks of anime magazines and video tape racks. he does a little drawing as well, and has some of his artwork displayed.
JoeSki hangs out at the Southside bars pumping Iron, with the rest of the boys from the mill.
Grasshopper is not ready yet.
monstro just destroyed Tokyo again.
Marley23 is waiting in line for a Christmas present from Scrooge.
**Airman Doors **is Jim Morrison reborn.
Bosda Di’Chi of Tricor in his natural form is a small blue tube. He takes on human form to study us a la Third Rock from the Sun.
Greenback comes out of the swamp at night to breed. He prowls around seedy taverns, looking for partners who aren’t choosy…
koeeoaddi is a Polynesian dancing girl, named for the call of a night bird.
plnnr talks through gritted teeth, making it tough to do vowel sounds.
The flame at the heart of a pawnbroker’s diamond is a Coldfire.
I wanted to see what other things people could come up with for my name.
Hey I know I’m kind of new here…but does anyone want to do me? Please?
…You know what I mean. 
Elenia25 is a young, blonde, Internet savvy woman who is the butt of many Scandinavian jokes told in Minnesota…
Alex, who are “Ole and Lena”?
Sigh…maybe I just don’t post enough, but I always read these sort of threads to see if anyone mentions me.
So far no one has.
Well, Jerrybear, your name makes me think of a Yogi bear type look, jaunty hat, tie, and growing hunger for a pic-a-nic basket.
Well, you got young (28) and Internet-savvy…
Thanks. You made my day. 
(Note to reader: we are talking about Scout1222 here.)
I do have several inches on her. Almost a foot, to be precise. Scout is a petite, very pretty marathon runner.