Well, for the pea brains in the group like myself, let's keep it pretty straightforward since we're already going into plate tectonics and that is a bit more deep than even I initially expected. :3
Plates move in one direction.
Technically plates move in arcs (which is why they seem to move in more than one direction). But yeah, for the simplicity of this game, we should use straight lines.
Really, once the tectonic plates are set and the mountains/trenches drawn in, I don't see them playing much of a factor in the game. If they're moving in 'multiple' directions, that really just allows us to place mountains/trenches where we want etc. However, I don't think that matters because based on Hydro's interpretation, the map looks like it has some pretty interesting stuff going on already anyway.
Goblins are literally my favorite fantasy creature 
And as for fantasy, it would at least be cool to have animals that don't exist, even if they're not fairies and stuff, we could take a sci fi approach and just have weird animals
I'm not opposed to woolly mammoths or giant sloths since they did exist in the same time frame as humans, but I'm iffy about anything beyond that. I could probably be persuaded either way.
I might be getting ahead of myself, but when we start looking at placing cultures in the Stone Age, I think it would make sense to have a ground zero for humanity and then migrate peoples away from that point. There could be several initial groups that move in different directions from ground zero which eventually branch further into more diverse peoples that settle the world. This could add some interesting backstory between cultures rather than just plopping people around the world and trying to come up with a creation story for how they got there.
And I definitely like Pat's idea for introducing disasters into the game. We'll need some crushing catastrophes in our history, not just constant forward progress.