The premine will primarily be focused on providing enough ENG to support the network as we grow. Fortunately this isn't an immediate need so we currently have the luxury of giving some time to let the market find a value for the tokens based on the current distribution model. That being said the premine will be split into a few categories that will be discussed further in some future announcements.
There's a number of avenues that have been looked at for advertising. It's all very new so I'm very open to exploring anything you feel might be interesting and has the value return. I just don't want to get any hopes up that we'll be able to do all things but are certainly open to great ideas!