First and foremost, it is a stylistic device some of us with enough knowledge of image manipulation use. As for why this particular filter was chosen, it is exactly for that reason you mentioned. Nomads do not have visual organs the way humans do. While our eyes convert a certain range of EM radiation wavelengths to assemble a picture we can view, Nomads 'view' differently.
The Nomads sustain themselves on radiation. Their ships are essentially like solar plants, able to absorb this radiation to convert it into useable energy, just as a human body breaks down food into energy it needs to sustain itself. Because of their dependency of radiation, they need to be able to identify how to find it. They need to 'view/perceive' it in some way. Thus if some object moves in space, it causes disturbances in this picture the Nomad perceives of the radiation around itself. The filter is just a crude way of approximating the general gist of this.
Thanks for the interest, by the way. Hope this explanation helped a little.