The box art includes a white background with a picture of a snow leopard, the same image on the product's disc. The front includes the slogan, in Portuguese, "The world's most advanced operating system. Perfectly optimized."
According to rumors that have been suggested Snow Leopard could go on sale as early as August 28th! There is no evidence to support these rumors, though.
AppleInsider | Apple Snow Leopard purported packaging pictures shown
Photos of Snow Leopard Disc and Retail Packaging? - Mac Rumors