Yes, is there some way of increasing the number of civilizations you can have on one map? Like lets say 20 something civs on a large/huge map. There's a 18 civs limit on these maps and I was wondering how to as if remove this limit and set a higher number.

There are several mods/modcomps around that increases the maximum number. If you know how to compile you can make the change yourself in the SDK, it's only one variable that you need to change, MAX_CIV_PLAYERS (CvDefines.h). Note that you cannot change the max in vanilla, only warlords.

Ok, I have another problem. I wanted to play/edit the original Europe map (the huge one) with a mod that allows 24 civs. But the game crashes when it tries to load the map. This maybe caused by the original number of starting locations - 18.

So, how can I get 24 civ to work on that map?

Copy/paste the map (so you don't overwrite the original), then open the copy in a text editor. At the start it says
BeginPlayer
LeaderType=NONE
CivType=NONE
Team=0
EndPlayer
Make there be 24 and not 18 of these. The last team should be 23 since it starts at 0.

You may also need to add more starting locations, I don't know. If you do they are defined where the plots are defined, like this:
BeginPlot
x=44,y=50
TerrainType=TERRAIN_GRASS
PlotType=2
StartingPlot
EndPlot