Actually, the feat covers armor and sates that you only have to be armed with a broadsword or arming sword in one had, leavging whatever is in the other hand open. You are limited to Medium armor, for which a shield qualifies (because shields do not affect a character's speed, Max Dex bonus or Dodge Defense). Further, the only real caveat to the feat is 7 levels of Barbarian, beyond the weapon restrictions.
I don't see any reason why a character couldn't use Intricate Swordplay while armed with a shield or other weapon, but I might apply the shield's Armor Check penalty to his attacks if I were looking for some sort of drawback for some reason.
The ACP is there for when you are not proficient with the armor in question, but there's no mention of shields in any of the armor proficiency feats (light thru heavy). But really, well trained swordsmen, like Roman Legionaires, could use a sword and shield very well together and really only had thier code of conduct to prevent them from mocking opponents, although I'm sure it happened. Also, because ZIngara and, particularly, Aquilonia are mentioned as sources of training in that "flashy western style", it would seem fair to say that shield use might even be common.