The podcasts on YouTube are a rapidly growing format that lets creators share their message and connect with their audience in new ways. Podcast creators get special video and playlist badges and are eligible for official search cards, and to be featured on youtube.com/podcasts. we’ll walk you through how to create a podcast in YouTube Studio and Thumbnail
What is Youtube Podcast Thumbnail Size
For Image size & resolution
Youtube recommend your custom thumbnails need to be square with a resolution of 1280 by 1280 pixel with a minimum width of 640 pixels and Be uploaded in image formats such as JPG, GIF, or PNG. Remain under 2MB for videos or 10MB for podcasts.
How to Upload a YouTube Podcast Thumbnail Image
It is very simple and Easy You’ll also need to add a square podcast thumbnail which is a unique requirement for podcasts. In YouTube Studio, you can see all your podcasts by going to “Content,” and then the “Podcasts” tab.

To upload the thumbnail just click on Create choose Podcast then Put your Title and Description, next click on Upload Thumbnail and that’s all

For more you can watch the Video here