Hi Matthew McCloskey,
I ran a quick test, and I was able to figure out how to delete an image from the Story Map Series.
First things first, is the image itself embedded in the text box on the left-hand side? If this is the case, you can click right on the image to "highlight" it. Once the image is selected, all you have to do is press "Delete" on your keyboard to get rid of the image. You'll know when the image is selected when you see the little black box in the bottom right-hand corner of the image.
I've attached a photo illustrating what I'm talking about. If you have any other questions, feel free to reach out!
Cheers,
Joe