I've customized the hell out of it (because I like the mod, it isn't too big and never lags for me). Here are some of the things I've done and if you'd like I can send you my work on it so far, I will tell you that I am not that good at doing this so its pretty "messy" (file/folderwise);
I changed the flags and colors alot, I used some of Rhye's flags and buttons, I changed the leaderhead buttons so they match the people. I changed Franco to Franco (instead of Castro's LH), I changed Gyges, Muwa, Taharqa, Solomon, the Inuit guy (I didn't like the purple), Deganwida, Caligula (I used Constantine because I am going to change him to Constantine), I changed Lorenzo, Lajos Kossuth, and Satur. I changed the Polynesian flag, the Lydian flag/color scheme (I used blue and yellow, and the flag now has a lion, which was Croesus' emblem), and the Sumerian flag (the one you used was for Aksum).
One thing I noticed was that the Marine unit for Spain (and whatever other countries share this unit type) had a blue beret, like a UN soldier. Is there a way to change the beret color to match the color of the the country? For Spain I used dark yellow and red, so the beret would show up as yellow, for Rome I used Dark Red and Dark Yellow so the beret would show up as red. Is this an easy thing to do or would I need someone with some graphic skills to help me do it?
I also changed the Mexican flag from the Austrian logo to the real Mexican logo (Eagle eating a serpent), but I don't have a button for it, so I still use the Austria button.
Thought you'd like to hear about those changes though, and like I said I can send you a zip file of what I have done if you want.