The sculpts are by Tom Meier, the one and only. Amazing work, as always.
You can see a lot more pictures on Dark Sword's website at http://darkswordminiatures.com/ Ser Gregor will also come with an alternate arm and head (sans helmet), so you can work him up as you see fit. He was helmetless when he faced his brother Sandor during the Tournament of the Hand, so a second diorama could easily be made with Mountain and Hound.
Tom is now busy sculpting Brienne.