Moderator Action: Moved to the Mac section.
I guess it is a problem with the combination of the weakest possible graphics card for Civ5 and the Mac system.
It's already in general suprising, that the animated leaders are working for you, i don't think other people with such a system can view them, the static low spec leaders should be a default there, i guess.
Maybe Aspyr will take a look at it, but i guess rather not, because i'm pretty sure it#s the fault of your graphics card.