Leonardo, because you do not mount propaganda images and display them on a Panel (or panels), switching to each Timer event.
You can read XML from anywhere on the internet with all the images and store it in the database (sqlite, for example), keeping it up-to-date in case your client goes offline. It counts the clicks by the application even incrementing some column and from time to time, sends the XML to its site to total, zeroing the local clicks.
If I were to do something commercial for Windows Forms I would think of something more or less like this. Years ago, I even did something like this in Delphi, following this line of thinking.