So, because I thought it'd be cool to have. Here's a 'Shield.Bmp' for interregnum, so it has a shield in Karei's Mod Launcher. This mainly just shows a Special Shield for it, you put it in the main mod folder, not in any of the Sub Folders.
I used the Austrias_Porto shield as the template.
Shield File
I used the Austrias_Porto shield as the template.
Shield File