Special use of might and could1 
i You were mad to drive so fast: you might/could have been killed.
ii We could/might be in Africa. [knowingly uttered in France] (Perhaps somewhere long abandoned in the south of France. I add this. Correct me if I'm wrong.)
These do not fall into either of the above major categories: there is no implicit condition, but the preterite conveys much more than a slight element of tentativeness.
In [i] the (circumstantial) possibility existed but was not actualised: you weren’t killed.
[ii] can also be regarded as unactualised circumstantial possibility, but differs from [i] in that there is no element of cause and effect (as your being killed was a possible result of your driving so fast); it can be glossed as “It is as though we were in Africa — we’re not, but judging from appearances there's no reason why we should not be”.
I'm more interested in the application of case [ii].
Suppose I am eating an ice-cream cone, and it tastes like caviar, can I say "I could/might be eating caviar."? (Apparently I'm not)
Suppose I forgot my laptop's password, but my sister somehow inadvertently got it cracked, can I say to my sister "You are so smart. You could/might be a Russian hacker."? (Apparently she's not)
Suppose I'm watching Luis Suarez biting his Italian opponent, can I say to my sister "Suarez could/might be a cannibal. Don't be a fan of his."? (Apparently he's not)
Would my remarks correspond with the context?
1. Page 201, The Cambridge Grammar of the English Language, aka CGEL.