Mods for MTW are quite numerous. If what you're looking for are mods that enhance vanilla MTW's gameplay, I suggest that you take a look at either BKB's mod or the XL mod. Both of these have added factions and units as well as a lot of other things which are designed to make the gameplay more immersive and also make the AI more challenging.

But if you want something that changes the whole of Medieval, Pike and Musket is the way to go. It shows the world as it was during the XVI-XVII centuries. It has new factions while keeping some of the old ones and it also implements cool new concepts which make the gameplay varied and interesting.

Those are the ones I've played(excluding BKB, but I'm sure it's also a mod worth the download and more) and there may be more mods out there that should satisfy your needs. As for the where to download, these can all be found in the downloads section of org or in the engineer's guild, where they have their own threads.

P.S. Noli Me Tangere eh?- "Touch me not". Have you read El Filibusterismo yet?