Spot the Ball

I currently require a web based application that allows me to enter a "spot the ball" competition on my website. This needs to be a grid where by the customer needs to identify where they believe a soccer ball has been removed from a picture in order to win the competition. The grid needs to be incredibly fine as I need to sell around 20,000 tickets per competition. i.e. the grid would need to a large number of coordinates available for people to choose from. To gain a better understanding of what I am trying to explain, please visit [login to view URL] and click on "buy tickets" to take you to the competition. Here you'll see the same type of page that I am trying to add to my site. When customers choose the grid, they also need the option of making multiple selections (guesses) and each time they make a guess it will need to be linked to a payment shopping cart. So that when they are finished making their selection, and proceed to payment, I need to be able to relate the coordinates to each seperate transaction. It may be the case that this project also needs a members area for this to be possible. At present I intend on using Paypal and/or Stripe as the payment processor, however this may change depending on legal issues with them. Ideally I'd like to see examples of similar projects before awarding the project.