This incredibly useful modding tool will allow you to add higher resolution portraits to your game, as well as switch between portrait mods easily ingame. You can press the P key to change portrait packs at any point when a dialogue box is open. The mod itself however does not include any portraits, why not try these?
1.3 Beta Download
Pre-1.3 Beta Download
Adding Portrait Packs
Navigate over to your Mods/Portraiture/Portraits folder. Create a new folder here for the portrait mod you’d like to install, name it whatever you’d like. Now download the portrait mod you want, and extract the files into the folder you’ve just created. All that’s left is to restart your game and talk to someone. Press the P key to cycle through any mods you’ve installed. This will work for as many portrait mods as you wish!