I love the idea! A cultural map of the world... I have to do something like this myself one day. Colours seem okay to me, they carry the message very well. I would try to make the "dots" less pixelated though, to make the colours look more natural and hand-applied maybe...? That is just a suggestion of course. To make the map more interesting... Maybe you can add to the poisonous hemisphere some awful, dangerous monsters that are roaming that area? Some sea creatures in the ocean? It would certainly make the cultural statement about the unknown parts stronger...