Here is the updated version of the pre-vis set model. I have added the outer platforms to the centre piece, and added a tube for the cell to go down so that they can start the Cycle again.
With the background, I used a "Cloud" texture, and used a dark & a pale red palette. I wanted the background to look like a generic sort of "flesh" texture, so that people could still somewhat understand that this was taking place inside of a person.
On each of the outer platforms will be a certain challenge that the Cell has to complete in order to pass onto the next section. The host will be standing on the paler tower that is in the centre of the set, acting as the "Overseer" character that Dr. Klappa described.
I am still unsure of the texture to use for the tube on the left. I was debating whether to keep it this texture, or to make it a shinier plastic kind of texture like the coloured sections of the rest of the set. I also do not know if I want to keep the texture used for the background, try to find something that gives off a better feel that this is taking place inside a person, or whether this current texture is sufficient enough in doing that.