Good evening Perch and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
I would love to help you with this topic.
You are right it does not look great.
However I do not believe that this is caused by the lack of images on some events.
It is a combination of the theme used, some settings and the uneven length of excerpts.
The simplest solution would probably be this one: https://theeventscalendar.com/knowledgebase/change-photo-view-to-equal-height-grid/
Let me know if that helps.
Have a great day!
Geoff B.