It always amazes me when a 2D image creates the illusion of motion. Twister by Renderosity artist OkrimSlava is a perfect example. The image is so well done that you can almost hear the wind whipping across the scene. Texturing in this image is also remarkable. It's not easy to create clouds, but add in the storm/hurricane element and the difficulty level goes off the charts. OkrimSlava does a beautiful job with texturing. The overall scene is compelling and beautiful.
Visit OkrimSlava's gallery at Renderosity.com. He has some truly awesome work on display.