My suggestion for new civs for the new map (sorry if this isn't the right thread for this, I'm new here)
Africa
Boers - I wrote some suggestions for them in the map suggestion thread, I can copy them here if you would like
Swahili - I have no suggestions for this civ's gameplay or unique elements, but I think it would be good to have, both to fill up coastal East Africa, and because it could have interesting interactions with Arab, Persian, Ethiopian, Indian, and Portuguese civs
Islamic Egypt - I know it shows up as a respawn of ancient Egypt, but it was a very different culture and civilization, and it would be nice if it was playable and had its own UHVs
Asia
Manchu - they could take over China in the 17th century, and have new UHVs that are different from China, they could provide interesting gameplay as well as making 1700 AD China a civ that can win UHVs (although in this case, China wouldn't be present as a civ in 1700 AD, only Manchus would, China could spawn again in the early 20th century if the Manchus are unstable)
Europe
Sweden - Scandinavia shouldn't really be represented by just one civilization - the Vikings can become Denmark-Norway once Sweden spawns
Kyivan/Kievan Rus - now that Eastern Europe has more space, they can fit in, and can be an interesting rival to Poland and Russia, they can respawn as Ukraine if Russia collapses to core in the modern era
Celts - it would be nice to have a playable Celtic civilization, it can respawn as the Kingdom of Scotland in the Middle Ages and as the Republic of Ireland in the Modern Era, although a color change would likely be necessary (Scotland is blue, Ireland is green, or you could split the difference and make them some greenish-blue intermediate color)
Australia - the only major post-colonial civ that is missing other than the Boers, it would be nice for Australia to be an actual civ instead of just staying a British colony for the entire game
Those are the only civs missing that I think are really essential
Some others, like Nubia and Israel, might be nice to have, but are probably too small to even include on the bigger map.
It might be nice to split Islam into Shia and Sunni, too, but I don't think it's that important, since the only Shia civs in the game would be Iran and Islamic Egypt.