Need Help with Adding a New Faction

Okay, so I followed Alpaca's advice, only to discover that I'm doing something horribly wrong, because my faction has no symbol on the flag above my armies and has no faction icon on the "Display Faction Scroll" button.

I attempted to simply add the symbols9.tga file from Crusades into the mod folder, but, as you probably know, the game references those images in a very peculiar way, so simply having the image available isn't enough.

Is there something I can do to modify the file so the game takes the image from that file, or do I need to keep treating it like a new image and hope that sooner or later I get everything done correctly?

I should point out that I'm incredibly new to modding and haven't touched a compiler at all in the past nine years or so, which means I know nothing at all about what I'm doing.

My brother is having some great progress on modding our map, and I've got my faction introduced as a playable one (although I have to hit "Continue Campaign" and then quit to create a new campaign - for some reason the game is crashing if I go directly to Single Player > Grand Campaign), but the images just aren't there. The symbol is displayed correctly above settlements though, and I have imported Knights of Jerusalem already as a unit with a working skin.

If anyone could help me out, it would be greatly appreciated!