The Licensing page says
With a Standard license, you may not:
I have licensed some images, standard license. I was trying to use them for the cover image on a puzzle book I am creating as a donation for a non profit.
Why do I need to by an Enhanced license? These will never reach the level of 500,000 uses because they are not for public sale.
The price of the license would increase my cost about $2 a unit and makes no sense.
While the image is being used on the cover, it is not the main value of the product. I use it only to depict the theme, which is waterpolo. The puzzles in the book are the primary reason for purchase.
Can you offer any resolutions that will help?
If you are just using an image on the cover you should be fine with the standard license.