Testing
Small build I used during testing. Shows flame jets over mature netherwart and from lava pools. Steam jets can occur over water blocks adjacent to hot blocks (in this case lava under the cauldron).
Morning Fog
Morning fog in Biomes O'Plenty redwood forest
Dense Biome Fog
Dense biome fog in the Biomes O'Plenty Ominous Woods
Fire Jets
Fire Jets spawn over lava source blocks. They do not harm the player or any mobs. The height and duration is based on the number of lava source blocks beneath the fire jet.
Steam Jets
Steam Jets will be generated around areas where lava meets water.
Waterfalls
Water that flows downward can generate splash particle effects as well as sound. The splashes are larger if the water falls a greater distance.
Large Waterfall
Naturally generated waterfall that I discovered wandering around in my test world. (The clouds are generated by Weather2.)