You can add it in any position of accs, but this direction will help you.
update\x64\dlcpacks\mpbattle\dlc1.rpf\x64\models\cdimages\mpbattle_male.rpf\mp_m_freemode_01_mp_m_battle
I tried to make it as simple as possible, being a cast on my arm, I made the typical drawings of friends and the odd one.
Credits:
Noviacadaver