Ah, well, I discovered some more looping errors - it is as if my corrected file isn't saved properly, very weird - so expect an update whenever I can find time to correct them once again. No problem though; I'm using your leaderheads for my own mod as well, and modding thrives on sharing, doesn't it?
On that note, I've started adding Umbar, Harad, Khand, and Rhun to my mod, and fleshing them out here might provide you with inspiration for yourself (or just use ideas I mention here, whyever not). I'm thinking of making Herumor the leader of Harad, and Castamir the leader of Umbar.
Umbar will have the Corsair as its unique unit, replacing the Privateer and capable of being the main naval unit of the era, instead of the Frigate (I've completely reworked naval balance - including Pirates, Privateers, and Sea Rovers! - so going into details wouldn't be useful). Their unique building will be the Haven; a Courthouse that gives a free specialist per Fishing Boat and Whaling Boat. 'Haven' can both be a safe place (/ place of authority; a Courthouse?) as well as a docking place for ships, and replacing the Courthouse allows it to be built even in non-coastal cities that still have Fishing or Whaling Boats within their borders.
Harad, of course, will have the Mumakil, although I'm not yet sure about its specifics, mostly because I've also completely changed the War Elephant's role (as well as the two unique units I have that are based on them; Khmer's Ballista Elephant and Carthage's Loxodonta - the Numidian Mercenary is now Numidia's unique unit). For the unique building, I don't have a name yet, and would like suggestions. It'll probably replace the Theatre and provide a culture bonus for each Plantation resource (and Ivory?), as Harad is a huge area with lots of different tribes / cultures, varying from Mesoamerican jungle cultures to medieval Arabian cultures.
Khand will probably have a Variag as its unique unit, replacing the Chariot possibly? Unsure about that yet, but its unique building will be the Yam (Mongolian, 'supply point route messenger system', horse relays), replacing the Broadcast Tower (because nothing replaces it yet) and adding a trade route and +10% gold. Or perhaps a Merchant specialist. Who knows.
It is said that Rhun provided lots of food to feed all of Sauron's armies, and that it had a huge trading network, so its unique building - again, no idea about the name - will replace the Market and give +1 food to all river tiles (but lose a small gold bonus that I added to Markets which doesn't exist in Civilization IV anyway). The Wainrider could be its unique unit, but more than that, I don't know yet.
Also, making a city name list is an endeavour that takes hours per civilisation for me (literally, yes), and while I'm not happy with Harad's list - all but the first dozen or so are random names I found in a list; I couldn't research anything about them - I'm happy with the rest I made. Mordor, Angmar, and Umbar (I gave them locations of Near Harad to flesh them out) have probably about three hundred city names in total (Umbar has more than a hundred, for example, and that is without including Harondor). As for Isengard, well, I couldn't find anything but the dozen or so I have, which is quite a pity. Certainly because I intend to add Rohan and the Dunlending as well, so Isengard can't use cities of them (using Rohan would be a stretch, but Isengard using the Dunlending list could work - except that I want to add the Dunlending as a separate faction).
I'll upload those sometime later, if you're interested. I still need to create Rhun's and Khand's list after all.
EDIT: Should I release my Middle-Earth civilisations for public use? I also changed your buttons (Saruman's hand, Sauron's eye, Angmar's fortress thingy symbol...) to make them more in-line with the ones Civilisation IV uses.