Small Portrait = Battle portrait? (One showing up in middle of the game)
If so, Dimentions: 48x56
After that, you gotta add them to their respective .PAC (Download the original Battle Portraits Pack around and then edit them)
Example:
FitZelda00 (Costume)
Character Selection Portrait for this one (Inside common5.pac) is called "MenSelchrFaceB.131"
Battle Portrait would be in "SD\Private\Wii\APP\RSBE\Pf\Info\Portrite" named "InfFace131.pac".
Sorry, but InfFace### is a BRRES file, NOT a PAC file.