Google offers this grey Nexus 7 case on its website: https://play.google.com/store/devices/details/Nexus_7_Cover_Dark_Grey?id=nexus_7_cover&feature=accessories#?t=W251bGwsMSwyLDExMSwiZGV2aWNlLW5leHVzXzdfY292ZXIiXQ.. (https://play.google.com/store/devices/details/Nexus_7_Cover_Dark_Grey?id=nexus_7_cover&feature=accessories#?t=W251bGwsMSwyLDExMSwiZGV2aWNlLW5leHVzXzdfY292ZXIiXQ..)
Asus has also said they will be making different cases and of course all the well-known case makers like Case-Mate, Otterbox, Marware, Boxwave and more will I'm sure come out with all kinds of covers and cases. Wouldn't be surprised to even see ones with keyboards as well.
(http://i.imgur.com/iEAC1.jpg)