Netro Mancer, the male leader, only appears in the base game (DL). Unless you are playing that, or changed it yourself, I don't see how he could be there.
Anyway, to change the portrait of the race leader:
1. For your own race: After you have selected the race you want to play, you come to the "Customize Your Civilization" screen (where you can assign points to different abilities, change the name of your leader and civilisation, etc.). In the top left corner you can see the picture of your leader. At the bottom of that are two small arrows, pointing left and right. Click on them to select a different picture.
2. For an enemy race: Once you've come to the "Choose Opponents" screen, click on one of the races you have selected as enemies, and then on the Edit button, right below the portrait. This will bring you to the "Customize Your Opponent" screen, where, as the name suggests, you can make several changes to that race. Just like with your own race, you can see the picture of the leader in the top left corner, with the two arrows below it. Once you're done, just click on Next to get back to the "Choose Opponents" screen.
One thing to keep in mind: You can make those changes only before you start the game. Once the game is in progress, they are permanent. Well, until the next game at least.
