I managed to get a picture of my room before throwing all my stuff around. It was taken with the 16mm fisheye and “defished” with Fisheye Hemi.

While the fisheye is not particularly suited for architecture, I use Hugin (open source GUI on top of panorama tools) to “defish” the images. The rectilinear projection (a standard lens is rectilinear) yields and horizontal angle of view of 129° (this is way too much for a rectilinear projection, usually limited to 120°) and a vertical angle of view of 86°. This is the equivalent of a rectilinear lens with a focal length of 8.5 mm horizontally and 13 mm vertically. Of course the 3/2 image ratio is not respected anymore, the corners are somehow soft due to extreme stretching and the objects on the sides have a crazy perspective, but these angles of view are so extreme that it opens a lot of possibilities.

I have to explore more on different projections and find a projection somewhere between the fisheye (too curvy) and rectilinear (too much perspective distortion).