A few ideas, off the top of my head

I've had a few ideas for some RTW mods, but as I lack even basic modding skills they will remain just that unless someone picks up on them:

Vampire: Total War
Nothing cheesy or Buffyesque. Based on White Wolfs pen-and-paper rpg Dark Ages: Vampire, this mod would be set in AD 1230. 13 Clans of Vampires rule the Dark Medieval night, and the War of Princes rages. Levied soldiers march towards unknown destinations at night, fighting and dying in conflicts they can't possibly fathom. The undead Monarchs of the nightly Vampiric nations rule the world when mortal men sleep, fearful of what lies in the darkness beyond the light of the torch.

Arthur: Total War
How about some Arthurian legend? A semi-fantasy mod set in a fairy-tale europe; low on magic but high on epic, where legendary heroes and brave and chivalrous knights meet on the field to do battle. Field armies of knights, recruit legendary heroes to your cause and surround yourself with powerful enchantments.
:charge:

Ten Kingdoms: Total War
Or possibly Warring States or Middle Kingdom, whichever is more appropriate. This is more of a dream than an actual suggestion. I love chinese history, but know far to little about it to actually make concrete suggestions here. Still, a project based around pre-imperial china would rock heavily! :bow:

So, these are my ideas. Make of them what you will. Just don't complain about how bad they are, or how I should try to make the mods myslef. theyre just ideas. ~;)