I'm calling these done. Well, almost - I've just given the undersides of the bases a coat of PVA to see if it helps to counter the warping. I also need to sand down the 25mm bases as they don't seem to fit in the 25mm washers.
There are two main types of swamp in New Guinea - mangrove swamps along the coasts and river mouths and palm swamps inland. I have done these, as you can see from the photos, as the latter. Giant ferns along the water edges are a common feature.
Here's a photo of all the insert bases:
There are 28 bases of trees (3 per 50mm base), plus five 50mm bases and fifteen 25mm bases with giant ferns:
Once the PVA on the undersides of the swamp bases has cured I will start work on the extra bases for bamboo thickets and kunai grass.