For future terrains I would like to see an Ice Field.
-Every grounded non Ice type gets his speed decreased by X 0,5
-Pokemon with Flame Body or Magma Armor don´t get their speed decreased
-Hail last for 8 turns
-Nature Power will be Ice Beam
-Water attacks now apply additional Ice type damage
-Rain Dance will change to Hail
-Eruption, Heat Wave, Lava Plume, Flame Burst will terminate this field
-Ice Beam will let this field reappear (only if it was terminated)