Yes “Pelvis and Rib Cage” can count as a “Pelvis”, so can a Pelvis.
For the moth-man pic it is either (wise or not Mothman).
for the Cultist Dagger, the Cultist Blade is also fine.
For the pictures: you need 4 people for the musical band one. All the rest of the pictures just need to be from 2 to 4 players (1 player alone is not enough)