What you are looking at here is a common problem in architectural vis. Most camera setups simply do not match the way in which the human eye sees a space and what may actually be quite a large corridor in reality suddenly shrinks down to nothing when you put a camera in to do a walkthrough.
The problem with playing with the lens sizes is that yes, it does work to an extent, but as soon as you start to move the camera you start to get curvature of straight lines. You really need to try and get a happy balance.
Sometimes, the key to increasing or decreasing the appearance of size is to work with light and shadow (as Coolhand has been saying - effectively, if you can't see the seen properly, you can't tell its size properly either). Even the most simple physical keys under the right light can help drastically. Play with your shadow softness (which, looking at your earlier renders, you can probably do as I get the impression that you are using some AO in there?). The softer the shadow, the
smaller a space will become. I still remember a specific button that you could press on the Inspire renderer (aka a LW variant) that would make the shadow softness super-hard for 'super large' objects, like planets.
On the one hand, try getting some long shadows in there as well to emphasis distance; but on the other, take a look at some of the architectural vis work at places like
CG Architect. SFM is good for SF, but a good architecturally dedicated site will help wonders as they are doing this stuff day in, day out.
Just as an example, I've attached a render of a large pyramid-like structure that I did about 2 years ago (Blender). You'll notice that without the sharp shadows going through the structure, this would just look like a model (not that is, that these test renders are anywhere near phot-real in the first place), while the 'soft' shadows at the base of the 'people' make them look far larger than they should be.