Well handing Excel the altered file does work... but why don't I take a sec to teach the man to fish?
From the start I'm gonna assume you know how to reach the Starsector game folder. Since putting mods in the game folder is the only way for them to work and you are.. well.. here. The mod site.
First go to the mod, "Oculian Armada" in this case, you want to edit in your "Mods" folder.
Open the "data" folder. -> Then the "world" folder. -> Then finally the "factions" folder. This is where who gets what portrait is decided along with some other things.
Your gonna need a program like Notepad++ in order to edit the files here. Its a free program and is literally just a buffed up notepad. Highly recommend it. If you don't have or don't want a program like that I'm afraid things end here. Otherwise on to the next step: Editing!
Left click on "ocua.faction" and "player.faction" and open them in your Notepad++ or similar program.
What your looking for is the list of "Portraits" near the bottom of the Ocua file. Its a short list it wont be hard to find. The player list has nothing but that list on it.
Now you have options; like just deleting the ones you don't want. They do need a portrait for both male and female tho so be sure to leave 1. It can even be the same 1 just copy it to both gender listings.
To actually SEE the portraits and determine the keepers go back to your mod file and look into "graphics" -> "Oculian Armada" -> "portraits"
In this case the 2 male portraits both work for not getting curb stomped by a red headed Miku. So you could just copy those 2 lines and replace the female listings with it.
"graphics/Oculian Armada/portraits/ocua_m1.png",
"graphics/Oculian Armada/portraits/ocua_7.png",
You can do the same for the "Player.faction" side. Or you can simply delete that file if you don't want those portraits yourself.
Another option you have is to copy a portrait list from the base game. You can reach those the same way you reached the mod lists. Just look into "Starsector-core."
Lets use Hegemony has an example. Just pull up their faction file and copy everything from the ""portraits":{" line all the way down to the "]," line and replace the same section on the mod file list. Now the Ai driven nutcases of the Oculian will all charade has upstanding hegemony officers in order to blend in with the rest of the gynocidal sector!
Finally you could skip text editing altogether and simply Replace the portraits you don't want from the graphics/portraits folder with ones you do like from elsewhere. Just copy the name of the portrait your replacing onto its replacement and swap them out. Just make sure the 2 portraits are the same gender or in game descriptions could get weird lol.
I could totally live with that too!