Updating main podcast artwork for The Bret Baier Podcast?

The URL of the artwork is carried in the <itunes:image> in the top part of the feed (before the episode information). To change it, assuming you are using a service to create the podcast rather than hand-writing it, you wojld need to subnit the image in the same way as you submitted the original image. If you are not sure how to do this, contact the service's Support.