Okay, so in the podcast where these things were discussed, it was decided that the Timeless Void should be bright, blurry, non-random, and that there should be color. As a professional news photographer, as soon as I heard these descriptions my mind immediately went to something that I have to deal with every day at work- overexposure. Here are a few examples from The Google.
In addition to blowing out almost everything with white, opening up the lens also reduces the range of focus of the lens (this is the science-y part of photography for those who don't have degrees in this stuff...) Reducing the range of focus causes the background to blur (or foreground depending on what you're focusing on) effectively killing two birds with one stone- very bright, out of focused backgrounds. It also allows for actual design and noticeable (as in "Hey, something's there!") features as opposed to an all white or artistically surreal interpretation of the Timeless Halls.
From a design and narrative point of view, this allows for structure. We have some place that the audience can conceive as 'beyond' yet is clearly identifiable as an actual location even if that location is not in the material universe. The extreme brightness will also contrast nicely with the empty blackness of the void. Narratively, even if we do play the Ainu as blind or unseeing, having the semblance of actual architecture and nature hovering in the background of these scenes lends to the idea of the Valar as sub-creators. What they are 'creating' in Arda is not of their own doing; the things they create are ultimately reflections from Iluvatar's mind.
From a production point of view (you know, that production phase that we aren't actually going to do...) this would allows us to shoot on locations instead of shooting everything on green screens and trying to create something mystical in a computer. It would also allows us some freedom in designs. We wouldn't really have the problem of creating a "God-Style" of designs and architecture because most of the details will be lost. With low-lit video you can boost the light artificially, brightening the image to see what is there in the shadows (which is totally what our fans would do when the show would hit DVD/Blu-ray.) If you boost a dark image it will be all grainy, but a lot of the details and color would still be able to be recognized. Counter-intuitively, when an image is overexposed by too much light, all of that information is lost- it never made it onto film/digitized into pixels. If you darken an overexposed part of a picture, it will just get greyer. All of the color and detail was gone the moment the light entered through the camera's len. [Rabbit trail: This is why, if you ever see a bad photo by a "professional", it's almost always underexposed. If it's completely overexposed, it's probably intentional for artistic reasons like in the images above.]
To take the design a step further, we could always mess with the sky and ground to make it more other-worldly. Or design the architecture and nature in unnatural ways/colors- keep it somewhat recognizable but experientially unfamiliar. Non-earthly designs would also help separate it from the typical depiction of Heaven (which seems to be portrayed artistically as surprisingly earth-like. I blame the Renaissance.) The only thing I'm not sure on is how the pre-Creation-of-Arda characters would interact in this environment.