The files are located in the info/portrite/ directory. These files basically consist souly of the .brres file. When you open it you only get a single palette and a single image for a single texture for that specific character. Simple enough, replace it with whatever new 48*56 image you wish to see in game. There are a ton of these though. There's something like 460 of them, so it will take you a while to modify them.