OMG... such simple matter, i have fucked up so hard.Those aren't mods. Put the image files in appdata\roaming\strive\bodies and appdata\roaming\strive\portraits depending on which of those they are. To actually use them with your slaves, start your save, go into slave customization, and use the full body and portrait buttons.
I'm not sure if the game does a good job of randomly assigning portraits and bodies. I've been trying that mod on the itch.io for this project that is supposed to assign portraits and bodies, so I don't remember if the vanilla game includes the random portraits checkbox. I haven't been able to get that mod working myself.
Thank you very much