Since the first time you are about to create the podcast, you can change the featured image for both Podcast Show and Episode image on the Confirm page.
If you want to change the featured image for your existing podcast show, do the following steps;
1. On the Shows page (Dashboard/Shows), click the Show you wish to update its featured image
2. Click the Setting icon at the top right of the Shows Banner. The project Settings window will appear.
3. You can now update the featured image and also other information of your show such as Podcast Name (Show Name), description, podcast categories (3 categories), host name, and your website URL.
4. Click Save. Done!