Ways to play vanilla.

[The Mouth]

Just wondering what some of you guys do to keep vanilla fresh since I wanted to play it one more time but I've run out of ideas that would want to make me play past turn 150-200... So far I've only really thought of doing a "Scorched Earth Policy" kind of thing and sending Europe back to the dark ages by destroying every single building in every single town I capture.

[PrestigeX]

I try out the mods, and give them a decent play through -- such that going back to Vanilla, feels comforting - fresh even - sort of forgetting the flow of the original.

I'm not sure about scorched earth... but it would be really fun to play a campaign and make your faction as Evil as possible - how ? well, always exterminate cities, always execute prisoners, use spies and assasins devotedly - tech up all those brothel line buildings to the max. KEep taxes on High, or Very High if you can =P ...
Weed out any purity in your ranks, try to get all your family members / generals to have dread points and be true buggers.
Pay no heed to the Pope, unless he gives you the opportunity to join in the fray on Crusade (ie. don't bother to stop killing if facing excommunication).
I would do this with a faction like Hungary only because they have 'battle field assasins' which kind of helps the 'role play' of evilness .

otherwise you could be the Moors (good start position, can get hashasins I believe, can do jihad, no pope - infact close enough to sack rome and kill his holiness )- i feel like egypt and turks are too noble, too worthy to be cast as 'evil' but .. lol thats just me.

[Stívarðr Reynitré]

Use only diplomacy. If you like battles, however, this might be a little less proactive for you.

It depends how radically fresh you want it?

[Silverheart]

Build an empire, then take a region on the other side of the map, migrate there, and gift your entire empire to as many random factions as you can.
The ensuing chaos of having some twelve factions battling it out can be quite entertaining.

Antoher alternative is that you simply do something challenging - defeating the entire Mongol horde in a field battle, taking over regions in a manner that provokes a metric s--t-ton of wars, trying to gain as many regions as you can through diplomacy, setting up a colonial empire, using only peasant troops in the entire campaign...
There are many options to make it more interesting and fun.

[CavalryCmdr]

Play as the Turks and not attack any AI factions until after the Mongol invasion

[Bonez]

Set completly screwed up goals like starting as England and migrating to HRE lands.