It depends on whether you want to play singleplayer or multiplayer i suppose. Prophecy of Pendor is a quite good singleplayer mod. As for multiplayer, you dont have that many to choose from. There are some mods which require Napoleonic Wars DLC, such as Iron Europe, then mods like Bear Force II, which work with regular old native. These are two of my favourites, but each to their own i suppose. You have quite a lot to choose from.