Often the older packs have active links posted near the end of their comments. I don't have recommendations about portrait packs, as I haven't bothered keeping up with the characteristics of each and whether they still have active links. The modding guide is in the 'Mods' section of the main menu and press the 'Help' button in the top right corner. They usually have one or both of the 'portraits' or 'bodies' folders inside them and you simply put them in the matching folders in the user data folder. The location of these folders is pretty much the same as the 'mods' folder, so I will simply refer you to the in-game guide to mods which explains where it is and how to access it through the game. The reason for this is that most packs were created prior to version 1.0 of Strive, when a couple of the elf races were renamed.
The vanilla game has random portraits, but it's a very simple system. Most(if not all) of the portrait packs are behind in versions, but they will work mostly right as is and can easily be modified to work correctly. They often have descriptive folder and file names, usually this is according to the tagging system established by the Improved Random Portraits mod. There are no 'portrait pacts', there are 'portrait packs', which are just folders of PNG(mainly these), JPEG, or WEBP images.
