That means they are approved for eventual use as a banner but haven't been assigned a date yet. It won't be until next year most likely as banners are already slotted through the end of the year. There are over 800, well actually that number includes past banners, there are some real active banner makers!
Most important think I think is make sure the images are in focus, blurry just won't do because the banners are prominent for 24 hours at the very top of the page.
