The Tropical Rainforest is a fairly rare, jungle-like biome. The vegetation mainly consists of Mahogany trees, with a few jungle trees mixed in. The ground vegetation consists of tall grass, shrubs , Orange Cosmos flowers and Poison Ivy. Wild Melons spawn in this biome just like they do in normal jungle biomes. Quicksand can also be found very frequently in this biome.
Villages can spawn in this biome as well (see the picture), although they shouldn't be able to with default config files. The spawning of this village seems to be a bug.