I am running the game on a 32MB NVIDIA GeForce2 420go card...
... game runs pretty smoothly. I get an eclectic mix of leaderheads.
Some render with a very flat surface. It lacks detail, but is easy on the eyes.
Most have a glossy sheen in parts (especially the faces); some like Musa and Kublai get a bit of a purple shine as if they're under a spotlight.
And Saladin and Louis have a super-gloss which whites them out almost completely.
As far as the black terrain -- if I set the screen resolution to 600x800, it will usually appear when zoomed in. But this is a "cheat" -- if you scroll around the map (zoomed in) you can see everything in the window as far as landmass (civs and their culture, et al will not appear). If you go global, you see only the land you've explored -- the rest is under fog of war.
I disabled wonder movies because they chunked out the system like woah.
Occasionally the leaders -- after time -- will slow down gameplay to a crawl ONLY when they contact you. If I contact them, it loads pretty quick. Sometimes they're a garbled mess... other times, they render. My computer picks and chooses.
Hope that helps.
-B