Hello,

There are already some options in the global options of the component (some options could be override from the menu options).

But not option for changing require concerning image upload.
Nothing planned to improved the submit an event form for 3.6.0, but i have planned to work on this part later, when the other part (list, event, and registration) will be full refactored (as older than the submit event view).

So, i will keep your idea about image required.

Don't hesitate to post other wishes as it would help me (i take notes of every ideas or requests!) when i will work on it (maybe in 2016, as i'm already busy with the 3.6.0 development )

BUT: if you know how to do an override of a component view in your site template, and edit php code, i can tell you where you can edit it to make this field required

Best Regards,
Cyril