The podcast artwork that Pocket Casts displays is supplied by the podcast authors.
- Go to that podcast’s page
- Long press the podcast artwork
- Tap Refresh Artwork
- Tap Profile
- Tap Settings
- Select Appearance
- Tap Refresh All Podcast Artwork
If you still see the old artwork after this, try clearing your device cache.
Some podcasts have per episode, and even per chapter, artwork embedded in their MP3s. If the artwork is embedded in the RSS feed it will not show. You can view this in the full screen player by turning on the following setting:
Profile > Settings > Appearance > Use Episode Artwork