There was a thread on this question sometime ago. My answer from there:

I've always pictured Omega like this: suddenly I'm pulled from our world and appear in a sterile white room that contains two boxes. At the same moment I somehow know the problem formulation. I open one box, take the million, and return to the world.

I've always thought of Omega as being pretty much the same as a comic-book character from my college days - Galactus. I'm not sure why exactly: presumably his god-like qualities, though his habit of zooming off to another galaxy before you pick your box(es) was perhaps an aural cue.

Now that you ask, though, I think a better model might be the character Q from Star Trek. I've never actually met Omega, but I'm quite sure he would have just exactly that annoying, in-your-face quality that I really hate in a minor deity.

I imagine him as being http://en.wikipedia.org/wiki/Omega_(Doctor_Who)

I visualize Omega as a blurry, grayish cloud of Utility Fog, which somehow appears to have a big, red Omega symbol hovering in front of it, no matter which angle you look at it from.

Omega doesn't speak, it plants the knowledge that it wanted to communicate directly into your head, so that you know exactly what it wanted to say, with no ambiguity.

Also, it has the ability to plant other thoughts directly into people's heads, including implanting whatever concepts the person needs in order to understand the concept of Omega, and whatever evidence the person requires in order to believe Omega's claims, and whatever other changes are necessary to prevent the person from having a mental breakdown when faced with the awareness that they are really talking to Omega.

Nope, don't tend to visualize it any particular way. It's just a part of the problem statement. I remember I once pictured it as a ball once in Newcomb's problem, but then I didn't next time.

I visualize Omega as a small black floating sphere slightly larger than a human head.

Do you imagine an appearance for Omega? A voice?

It isn't a definite image, but it is a rather big robot (10m high or so) with a not so big spaceship (both metallic and predominantly silver), with transparent boxes full of dollar bills. It has a normal male voice, probably cultivated, like an actor or TV star. I have not decided which language Omega speaks. Strangely enough, although the appearance of Omega can vary, I always imagine meeting him on two places not far from each other: first one, second one. In the first spot, Omega is physically bigger and presents the traditional Newcomb scenario or its variations. In the second one, there is a more advanced and smaller version of Omega (it's a rather narrow street, after all) engaging in counterfactual mugging and that stuff.

This cropped up on one of the open threads a few months ago.

I imagine Omega to be a large hovering red sphere with a cartoonish face and black Beholder-like eyestalks coming off in all directions.

I visualize Omega as a Culture Mind, either disembodied or as an avatar. A Culture Mind is about as close to omniscience as I've ever seen convincingly portrayed, so that image works well for me.

I "am aware of" Omega as a hyperturing Superintelligence. Something with the complete physical laws of the simulated universe, the very long string of random numbers needed to determine a specific universe, and the uncountably infinite amount of computing power needed to make predictions easy.

So I don't visualize Omega, it justs exists somewhere out there in the multiverse as something that doesn't have a form that I can visualize. It can only be specified.

A hypothetical construct created to explore philosophical edge cases and cause paradoxes (or mathematical, ahahaha, singularities) rapidly turns into nonsense when people claim they would believe its existence rather than the more obvious first assumption that an entity making such claims is a conman or mentally ill.

If you have reasoned yourself into such a position that you would believe in a suicide rock rather than assuming it was the work of a human, or that an entity claiming the powers of Omega is possible rather than the work of a human, then you have used the tools of rationality to make yourself mentally ill and less capable of self-care in the real world.

I visualise Omega as an underlined space __ in a word problem.