I agree with Rusty.
We have a mountain here referred to as "la mujer dormida". We would never say "la mujer durmiendo" or "la mujer durmiente". We don't expect the "woman" to wake up or change her state, I'd say that is why we use the past participle here.
Also, we translate the name "Sitting Bull" as "Toro Sentado". In this case, maybe we should have said "Toro Sedente" (bull in a sitting position), but the adjective (in this case, the present participle), is almost exclusively used in ancient texts or poetry.
I suppose here we still think of the state of the bull rather than his action to sit down.
I can't think of a "rule"; it will all depend on the context, I guess.
