Is anyone still doing this part? If not, I'd love to have a crack at it.

If so, I've got a few geographical/hydrological suggestions. The bogs or swamps make absolute sense, especially with that big area of water, but that looks like a shallow Lake Okefenokee to me more than an inland sea. Thus, I'd propose that there be a large river running mainly north-to-south out of area 3 (I'll check this in a moment; if not, maybe out of Terra Incognita to the north), feeding the Thrubmorton Fens to the south and also leaking some water into the two lake areas. The area around them would then be a bog, with slightly higher elevation. What do you think?

Second, the piece of land running from center north to southwest should be more mountainous, based on what area 1 looks like. This should be a bit of a mountain spine, not necessarily very tall but at least elevated above the bogs in the center south.