OK... I managed this one just fine. Probably because I was able to eliminate a lot of AI very early and was able to win before 1000AD, so I avoided the computer graphics overload crash.
Strategy: I followed some advices here... no need to re-invent the wheel.
I used max opponents to reduce dom limit and increase number of cities I could take, added all easy pushover civs (Indians, Egyptians, Americans, etc) to the required ones. I used snaky continents, with high seas, to reduce the amount of land area to a minimum (and make those pushovers even closer). I did not build any settlers early; my initial cities I was able to take from AI. In the the AD years I was just whipping settlers to fill out land. This delay in settling my continent worked well because the barbs tend to settle the huge tracts of fogged land on my starting continent, which are just free settlers, basically, since they defend with a single warrior.
I did an Oracle CS sling and stayed in Bureacracy until I got to Liberalism and then went into Free Speech to expand borders fastest. HR for happy, and slavery for production (I slaved out settlers mostly near the end, could have won faster if I slaved more units, probably).
I had eliminated all AI on my very large starting continent (5 or 6 AI) taking average 2 cities each, though admittedly the first two were eliminated by walking my starting warrior into undefended capitols. Amsterdam was coastal and built the Great Lighthouse, which is probably the most important wonder to get, but I also got Colossus which was kind of so-so since I didn't built workboats at all, except for maybe an initial explorer. I whipped courthouses in all the captured cities until about 1AD when it was just sprint to finish.
I was going to get Astro for liberalism, but by then my research rate was so high I just teched Astro in 3 turns, and ended up taking Rifling from Liberalism. I turned off research after Mil Trad for cavalry... but honestly that was a gigantic waste!
Engineering (for movement, though trebs helped not lose many units --since I wasn't making lots, that was important) when taking cities, was a key tech.
Optics (circumnav and needed for astro)... though why I built so many (4) caravels I can't justify... the East Indiaman was the workhorse here, and was available very quickly after Optics.
Astro was critical (high seas, remember?). I probably would have won quicker going for
Guilds quicker (just did it on way to Repr Parts)... Knights is what you should really use for this one, cavs are overkill and more expensive. Only AI units ever met were warriors, archers, axemen, warchariots, and swords. Knights were more than enough. But of course, its nice being able to take an entire continent with only the four units you can fit on a single East Indiaman.
At the end, it was a toss-up if I was gaining teritory faster by conquest or by settling the unsettled regions. Its weird to me to choose city placement based solely on how many land tiles in the BFC rather than the terrain (lots of iceball cities at the end). Planted cities could pop borders to 21 tiles in 1-2 turns with 50% culture on slider and Free Speech. No need for castes. Never had financial difficulties... too lean on units I guess (and whipping courthouses in the first half of the game, and the GLH).
One mistake I made was assuming the Great Wall (once captured) would allow me to leave all my cities empty... nope, only the ones on the same continent as the Great Wall.
Funny... I left a lot of cities undefended next to barbs that never went after the city, which is why I thought the GW protected me... nope, just lame barbs. Had to recapture a couple from barbs due to that... but warriors die easy. The "No city razing" option was therefore a blessing for this game, not a curse.
My off-continent conquests were done initially with Macemen, who are twice as slow as knights, I might mention. Fortunately, the AI build in clusters, so four mace can take a whole civ. I stopped bothering to wipe out the last units for "complete kills" since leaving the civs alive didn't affect anything in new captured cities that I could notice.
Paper was useful for getting maps to find the enemy.
Education was less useful... I built one university in capitol... that's it. I used my only GSci for a golden age (with a GPro) that was powered by Mausoleam of M... but I ended with 4 turns left in golden age so that MofM was a waste, too. I used my first GP (a prophet) to make the confu shrine... but never spread confu so it would likely have been better to settle him, at least short term. I guess I was hoping to spread confu that way, and thus gain some happy, so my units could do something more useful.
I think golden ages are best use of GP when you have so many cities, but I only had 2 golden ages. Didn't get many GP. Never finished the Taj.
Not much more to say... I don't play settler much, so its hard to judge where I could streamline more. I think a BC win is possible under proper conditions played well.
Patience is very important... it is easy for someone like me who likes to play fast to miss the best whip opportunities and build stuff in cities that are too far away from the action to be quickly useful. I'm happy to have beaten the best showing posted thus far, but still don't think I played my map as well as I could have. I mean... how was I to know that the last city I would capture only required one knight to defeat a lone warrior?
Lots of workers is good... improve best tiles and chop. Can never have too many... and fortunately they are easily captured.
I can't really say that victory was a challenge, but getting the logistics right surely is. So have fun! (And be patient!).
Edit to add: By the way, this is the FIRST Huge map game I have ever completed!
. As a side note i noticed i wasnt getting charged for colonial maintainence, is this a result of turning of vassels?.
-slider even new cities can get to 2nd border pop very quickly. I finished the game with 65 cities (4 of which were still in revolt). Several cities were redundant by the end of the game, but on Settler difficulty 65 cities is affordable without courthouses (only built 1 on accident). 
