There are plenty of different mods. Many have complete different feels and focus on different time periods.
(My personal favorites)
1) New Elgante : This is an interesting mod adding different animations and sounds. Its a complete overhaul, changing the map, the building structures, the factions (etc).
2) Roman invasion : This one shouldnt need too much explaining. It focuses on the Romans. . . Surprise!!!
It replaces the factions of Swadia with The Roman Empire, and replaces the Nords with the Gauls. It adds new items as well.
3) If you're looking for a way to spice up the multiplayer, I would recommend you check out the Bear Force mod. This is a multiplayer mod only that completely changes the multiplayer into an exciting starwars fps/tps experience. The closest thing to battlefront in M&B.
Quick list of runner-ups.
Native expansion
roman invasion 2
nord invasion (multiplayer)
Rome at war
warband enhanced
wild wind (multiplayer)
world war 1.2 (multiplayer)
WW2 China Battlefield
Blood and steel
Gekokujo
Have fun in the game =D
Hope this helped