The MacBook has a whole sub-culture devoted to just the customization of Apple products to reflect their own personality. Online stores like Etsy are often where you can find these handmade offerings such as this one of Steve Jobs, the Chief Executive Officer of Apple.
This self adhesive vinyl decal is specific for the 13-inch MacBook and has been designed to last some 7 years which in all likelihood will be longer then your MacBook considering the rapid pace of change that technology is undergoing. The decals come with a black background though other colors are also available. Retail price is $13.99 plus shipping.