- Upright (the way we walk)
- Upside-down (like some criminals are hung during torture)
- Lying head-up (sleeping with chest facing the sky)
- Lying back-up (sleeping with our facing the sky)
I went to Wikipedia and (briefly) read the following articles - Sense, Equilibrioception, Proprioception, and Aircraft attitude. Although equilibrioception and proprioception appear remotely related to body orientation, they don't seem to nail the concept completely.
Hence, I believe that body orientation should be considered as a physiological sense (if it's really not covered under the currently defined senses), since we seem to possess the ability to determine our body's absolute orientation (w.r.t. the earth's surface).