Excellent work, thanks for doing this.

Out of curiosity, why would you have a checkout process to simply download an image in the first place?

I'm a marketing type guy, so I'm very focused on gathering as much user data possible for anything I create. Sort of the "If you can't measure it, then it doesn't exist." philosophy. By adding a checkout process, I can gauge an approximation on the number of downloads.

Don't you have serverlogs/analytics for that?

The server logs might indicate how many times the image was loaded, however they do not reveal the number of attempted downloads.

Unfortunately this measuring method could discourage the people from downloading and thus could affect the measurable quantity.