I just ran across Flowstone Flood as an possibility for this deck. The buyback option could be nice. And maybe Frenzied Tilling though its a bit expensive to cast. Helldozer could be usefull too, but again he's pretty costly to cast. Rain of Tears could work. 

Winter's Grasp is green, and there's no green mana!  If you want creature land destruction, look at Army Ants, Avalanche Riders, Fulminator Mage, Goblin Gardener, Orcish Settlers, or Ravenous Baboons.  If you don't want creatures, some other goodies: Roiling Terrain, Seismic Spike, Sink Hole, Poison the Well (or Melt Terrain), Molten Rain, Pillage, Rancid Earth, Stream of Acid (or Wrecking Ball), or Lava Blister - all pretty decent and either cheaper than stone rain or multi purpose. 

See if you can't get a couple "Winter's Grasp" for this deck.