WET TROPICAL SAVANNA.
a biome with wet lands a and grass,lots of mud,water,maybe aquatic plants,very moist climate. this is a biome commonly found in the South America
DRY TROPICAL SAVANNA
another alteration to the savanna biome commonly found in South America with a dry tropical feel
TROPICAL CANOPY FOREST
a dense tropical moist broad leaf forest with many aquatic lakes and ponds,a wet and humid climate,lots of rivers,lakes and diverse plants and villages common,This is a biome from South America
TROPICAL MANGROVE
costal mangroves that spawn along the shore,very common in central,and south America,has a moist ,humid climate.
RIVER BASINS
a basin of rivers with a connection to the sea by a delta or river mouth,mangroves and marshes common there and on its shores, Tropical savannas ,and canopy forests
NOTE
all biomes found in the neotropical zone of south america

Wet Tropical Savanna - This would not be realistic as savanna's have little moisture, which is why you seldom find trees there. The type of biome you are describing is a swamp, bog or wetlands.

Dry Tropical Savanna - Our current savanna biome is pretty much what you are describing in this one. It is a grassland with a few trees, which is what a savanna should be.

We add a rainforest biome, which sounds a lot like what you are describing.

Tropical Mangrove - we have talked about adding mangroves but haven't decided yet. They aren't just a South American thing as there are several places in the US that have mangroves as well.

River basins - something we are already working on, however, before we can add them, there needs to be better river generation in Minecraft. Our coders are trying to figure out a way to get them to appear more realistic, but according to them and other mod authors that do terrain generation, it is not an easy thing to fix.

We will be making many changes to our existing biomes as well as adding many new biomes and terrain features in the coming weeks and months. We have a lot of exciting things planned.

What I mean by a tropical savannha is a tropical moist grassland with rivers, marshes, and a swampy area. They some times refer to it as a wet savannha. It is neotropical not the one you find in Africa. This biome is part of the make up of the amazon basin in South America . As for a dry savannha another version of a neotropical style biome not the one found in Africa. It would be be cool to see some neotropical biomes in the future. Neotropical as in the tropics of the Americas. For the rainforest would it be possible add sub biomes such as more tree types, plants,wetlands, rivers more common and maybe different heights such as sea level to cloud level with mountainous forest/ cloud forest is what they call it. And for mangroves that would be a cool. Sub biome for rivers in tropical regions as well as costal warm regions. I hope the river thing works out. I am thinking of a linking of rivers with different biome categories such as tropical , dry , or temperate that lay on the river banks. The basins could all be connected to a mouth or delta that flows into the sea. Tropical river basins is what I think in my opinion would be really cool. I can't wait for future updates!! Keep up the good work

Many new biomes will be added in future release, including more tropics.

Thanks for your interest and suggestions.