The faction leader needs his portrait assigned in his descr_strat line. The portrait needs to be a custom portrait.
Example form RotK:
Code:
character J-0201-LiuBei, named character, male, leader, age 33, x 151, y 128, portrait A132, label LiuBei1, battle_model liubei_general
The small pic is 49*63
The larger pic is 69*96
All of this is described in my tutorial, in the 'Using the Portrait\Individual' section.
If you wish to use the portrait in the faction selection screen then check the pic underneath, note the size and naming syntax