Well the only one in in the three mods I mentioned that adds different eastern european factions is Eras Total Conquest, and each time frame has different ones:
970: Hungary, Poland, Bulgaria, Serbia, Croatia
1080: Hungary, Croatia, Poland, Serbia
1200: Hungary, Poland, Bulgaria, Serbia
1300: Hungary, Poland, Serbia, Bulgaria, Lithuania, Teutonic Order
1400: Poland, Hungary, Serbia, Teutonic Order
1500: Hungary, Poland, Teutonic Order
1547: Austria, Poland-Lithuania, Prussia
There are more campaigns than that, for the e-european countries, and there is many more factions in each era in the game, I highely recommend Eras Total Conquest if you're up for actual historical factions. Just visit this web address to find out all the features, factions and etc. for Eras Total Conquest, that wikia also has a lot more info on other mods in the Total War series as well: http://www.twcenter.net/wiki/Eras_Total_Conquest
970: Hungary, Poland, Bulgaria, Serbia, Croatia
1080: Hungary, Croatia, Poland, Serbia
1200: Hungary, Poland, Bulgaria, Serbia
1300: Hungary, Poland, Serbia, Bulgaria, Lithuania, Teutonic Order
1400: Poland, Hungary, Serbia, Teutonic Order
1500: Hungary, Poland, Teutonic Order
1547: Austria, Poland-Lithuania, Prussia
There are more campaigns than that, for the e-european countries, and there is many more factions in each era in the game, I highely recommend Eras Total Conquest if you're up for actual historical factions. Just visit this web address to find out all the features, factions and etc. for Eras Total Conquest, that wikia also has a lot more info on other mods in the Total War series as well: http://www.twcenter.net/wiki/Eras_Total_Conquest