Okay, so as a bit more advice: you don't actually need to replicate the entire faction file when adding new portraits to the game.
.faction files in mods can, in fact, be additive; you can include only the data you want to append to the faction as it appears in, say, starsector_core, and it'll be added with no fuss by Starsector's executable. In fact, it's generally better to do it this way, because people may have messed around with their .faction files on their end or in other mods.
So the "clean" way to do the player.faction file would look like this:
{
"portraits":{
"standard_male":[
"graphics/portraits/m_01.png",
"graphics/portraits/m_02.png",
"graphics/portraits/m_03.png",
"graphics/portraits/m_04.png",
"graphics/portraits/m_05.png",
"graphics/portraits/m_06.png",
"graphics/portraits/m_07.png",
"graphics/portraits/m_08.png",
"graphics/portraits/m_09.png",
"graphics/portraits/m_10.png",
"graphics/portraits/m_11.png",
"graphics/portraits/m_12.png",
"graphics/portraits/m_13.png",
],
"standard_female":[
"graphics/portraits/f_01.png",
"graphics/portraits/f_02.png",
"graphics/portraits/f_03.png",
"graphics/portraits/f_04.png",
"graphics/portraits/f_05.png",
"graphics/portraits/f_06.png",
"graphics/portraits/f_07.png",
"graphics/portraits/f_08.png",
"graphics/portraits/f_09.png",
"graphics/portraits/f_10.png",
"graphics/portraits/f_11.png",
"graphics/portraits/f_12.png",
"graphics/portraits/f_13.png",
],
},
},
And that's all you need! There's no need to replicate the rest of the stuff in the base .faction file. What's above will parse just fine, so long as it's in the initial set of {} tags.
As a result, it's also fairly easy to just copy-paste it for each faction you want to add portraits to. Giving indeps, scavengers and mercenaries access to these portraits (e.g. they usually have access to portraits the player does) is as easy as taking this player.faction file, copy-paste it in file explorer, and rename each file independent.faction, mercenary.faction, and scavengers.faction. It's a similar process for other factions, albeit I'd imagine you want to curate the choice a little depending on context.
You can even add factions that aren't actually enabled otherwise - if you put a diableavionics.faction with this listing in /data/world/faction, and a player doesn't have DA installed, the game will just cleanly ignore it with no errors. And if it does get enabled later, the portraits will smoothly integrate with no need for further fiddling!
Anyway, this really is a well-put-together portrait pack, and .faction files aren't quite as intimidating as they look.