If you're interested in playing an Eastern European MTW campaign, I would download the MTW XL Mod. Instead of just Russia, Poland, etc. the XL Mod adds Novgorod, Kiev, Lithuania, the Cumans, the Volga Bulgars, Sweden, the Teutonic Order, Bohemia, Bulgaria, Serbs, etc.

It also uses a new map that adds eight additional provinces, including Estonia, Greater/Lesser Poland, Levidia, (and maybe one other) in the East. It's a better map, and provides the extra factions with the additional room they need.

I recently played a couple of great campaigns as Kievan Rus and Lithuania. The new map, factions, and units make the game much more interesting, particularly in Eastern Europe.

Highly recommended.