Hey wizo,
Thanks for using our plugins and welcome to the forums! Let me try to help you out here.
Out of the box it is not possible to have different images or image sizes on the different view.
With some customization though, I think that could be easily done, however we are limited in supporting customizations, but I can show you in the right direction.
One thinking is doing it with the custom fileds. Adding the image link into a custom field with a unique field name. Then overriding one of the templates so that instead of the featured image, it pulls in the image entered in the custom field.
Here is more info on how to use custom fields:
https://codex.wordpress.org/Custom_Fields
And here are two articles about overriding templates in The Events Calendar:
https://theeventscalendar.com/knowledgebase/themers-guide/
https://theeventscalendar.com/knowledgebase/template-overview/
I hope this helps you get started. Let me know if you need anything else.
Cheers,
Andras