Below are examples of my experiments, each with variations in fog density, colour and the size and shape of the containing Volume Primitive. Some examples are far more atmospheric than others, but either way I am pleasantly surprised with how much of a dramatic impact this simple addition makes.
The first two and last examples are particular favourites of mine, as they add a considerable amount of atmosphere whilst successfully masking a large portion of the environment. I will aim to add a bit more density in places to mask certain areas more efficiently, however, paired with adjustments in depth of field and the use of very tight camera angles, this may not be as necessary as initially perceived.
As for lighting, the single source of natural light (the window) adds atmosphere in these shots, although it is not hugely practical. I will likely employ what I am calling 'illogical sources of light', by which I mean, light sources that exist purely for practicality, with no logical origin. In terms of additional, practical atmosphere, I may add some 'Shallow Grave' lighting, referring to the lighting of the scenes in the attic. Examples of what I mean by can be seen here and here.
As well as these experiments, I have also been continuing to texturing the existing assets. Specifically, I've been aiming to have all assets for the first scene ready to go within the next day or so, allowing me to start animating the opening this week.