It was mentioned here with the fix. https://forums.elementalgame.com/443585/page/1/
But I'll post the fix again.
Okay I looked through the files and saw that the head on the generic slave has been set to
But under the CoreClothes the model K_Male_Head_03 does not support the SlaveMale unit type. That is actually the scion head instead.
Here is a fix for those that need to have custom designed SlaveMen drop this .xml file into your items folder in the documents end.
to the K_Male_Head_03 item type art def.
(Note you have to restart the game in order to see the effects).