So, from my reading of existing case law regarding doing things like copying poses... I think the only place you'd have an issue is if the poses you were copying were so distinctive that the poses themselves were actually a substantial distinguishing figure of the work. So something like the poses in "The Last Supper" might be sufficient for a copyright claim, but using as a reference an image of a few people in a relatively unremarkable pose that isn't intended as the focus of a picture shouldn't even come close.

I would not fret overmuch about this!