Wow, if he takes on all this, it's never going to get released!
Personally I like the marshes - if there's a problem with them it's the fact that they seem to overlap the surrounding trees a bit, which looks wrong, but again is a problem with how the game handles overlays (like the rivers). This problem could be solved by simply making the marsh graphic a bit smaller, but then it might not look so good when you have several of them next to each other.
I think the jungle, as it is, is one of the best elements of this terrain set. None of these things is to scale with each other as it is, so they may as well all look as nice and detailed as they can.
Personally I like the marshes - if there's a problem with them it's the fact that they seem to overlap the surrounding trees a bit, which looks wrong, but again is a problem with how the game handles overlays (like the rivers). This problem could be solved by simply making the marsh graphic a bit smaller, but then it might not look so good when you have several of them next to each other.
I think the jungle, as it is, is one of the best elements of this terrain set. None of these things is to scale with each other as it is, so they may as well all look as nice and detailed as they can.