Disclaimer: i haven't tested the texture packs or directx 7 myself. Use at your own risk.
1) enable 'show framerate' in the warband launcher
2) ingame, set detail to medium
If you're still getting unplayable framerates (for me, anything below 40 fps feels 'unplayable'):
3) set detail to low instead (make sure character shadows are off and corpses are set to 0)
If that doesn't help enough:
4) use the low res texture pack:
http://forum.c-rpg.net/index.php/topic,5335.0.html (hasn't been updated with many of the new textures, but will still help framerate a bit probably)
And maybe:
5) cRPG-optimization: http://forum.c-rpg.net/index.php/topic,6967.msg108140.html#msg108140 (Do not use. Already added to cRPG, also: might break it.")
And if that still doesn't help enough:
6) Use scarymod: http://forum.c-rpg.net/index.php?topic=6968.0(Not compatible)
And ofcourse you can:
7) switch to directx 7 in the warband launcher
That is what i could find just now with a few searches. Did i cover all the possible tweaks? Anyone actually used all these together?