Wrong generated images on free event

WebinarPress is currently designed to do this:

When an Admin creates a paid event, a new product is automatically created in WooCommerce. On the product page at WooCOmmerce, an individual product image can then be uploaded for use in the overview. If an Admin creates a free event, no product will be created in WooCommerce, because no payment process is necessary. This eliminates the possibility of uploading an individual product image that can be used in the overview.

So the main question is: how can we manage to upload an individual event image in WebinarPress independently of WooCommerce, which generates the image for the overview?

In WebinarPress you can upload a cover image, though. However, this image will only be used as the header title image on the individual event page.