You aren't very clear with exactly what you want, but my best guess is that your user will upload an image, and you will display that image on other pages as an advert for a period of time, after which you will stop displaying it.
Simple.
You have a database table containing the images (or pointers to them, however you are storing them) and two columns on that table define the start and end date (and time) of the 'campaign' the user has paid for.
In the SQL that retrieves adverts, you limit it to adverts that are currently 'live' - i.e.
where GetDate() between startDate and endDate
so you will never display adverts that are expired (or haven't started yet)