Hello there, Eusebiu! Thanks for getting in touch.
Yes, the main calendar is a post archive rather than a page, as far as WordPress terminology goes. That’s why you wouldn’t necessarily see it in your list of Pages in WordPress.
You can customize the archive by customizing the template of the calendar itself. Here’s more information on how to override and customize the calendar plugin templates in our Themer’s Guide.
Another way to add an image to the template is to do so in the Events > Settings > Display screen. At the very bottom there is an “Advanced Template Settings” section that allows you to add HTML both before and after the event content. This would allow you to add an image to the template without touching the core template files.
Does this make sense? Will this work for you? Please let me know. 🙂
Cheers!
Geoff