Hi Roxanne. Thanks for your detailed question.
The checkmark PNG comes from the public function getEventStatusIcon method in this file: /wp-content/plugins/the-events-calendar-community-events/src/Tribe/Main.php
I don’t see any filters in there, but you could suggest/request it via our UserVoice page.
Adding it there allows others who are interested in that feature to easily voice their support. We frequently review suggestions there to find out which ones are popular, then we implement as many of them as we can.
Once you post it, feel free to link to it from here in case anyone comes across this forum thread in the future.
Thanks.