Personal project. Always wanted to make four arms anatomy. In my opinion, one way it could work is if upper and lower arms act in different planes, fulfilling different functions rather than just duplicating each other.
Come and run with the crows and me
la Muse malade
Crow Skull Mask by ~Jennie-Wolf on deviantART
Demon/Satanic special effect makeup. Perfection. SFX prosthetics and accessories