One of Digital Podcast’s user community asked “Can you please let me know what size, shape and formate of image we need to use for upload with podcast material?”
You can include images with your podcast by adding image tags to your RSS that point to a URL where your image is hosted and by including the image in the mp3 id3 tags.
I suggest using a 300×300 pixel image of jpg or png format. You need to include a link to your image in your RSS via the itunes:image tag. You should also include an image in your id3 tags for each mp3. To add artwork to an episode using iTunes, highlight the episode and select “Get Info” from the “File” menu. Click the Artwork tab. Then click “Add,” navigate to and select an image file, and click “Choose.”
If you need more information:
Apple’s standards for podcast images using the itunes:image tag are as follows:
This tag specifies the artwork for your podcast. Put the URL to the image in the href attribute. iTunes prefers square .jpg images that are at least 300 x 300 pixels, which is different than what is specified for the standard RSS image tag.
iTunes supports images in JPEG and PNG formats. The URL must end in “.jpg” or “.png”. If the itunes:image tag is not present, iTunes will use the contents of the RSS image tag.
If you change your podcastÃ¢â‚¬â„¢s image, also change the fileÃ¢â‚¬â„¢s name. iTunes may not change the image if it checks your feed and the image URL is the same.
Spend some time developing an attractive, original image that represents your podcast well. Potential subscribers will see it on your podcastÃ¢â‚¬â„¢s page and a much smaller version of the image in search results and feature placements. Make sure your design is effective in both sizes.
The itunes:image tag is not supported at the item level. It is possible to include art within individual episodes, but the art is included within the media fileÃ¢â‚¬â„¢s metadata, not in the RSS feed. To add artwork to an episode using iTunes, highlight the episode and select “Get Info” from the “File” menu. Click the Artwork tab. Then click “Add,” navigate to and select an image file, and click “Choose.”
More iTunes tag specs can be found here
As for the RSS standards, I believe that the standard for a regular RSS <image> tag is 144×144 pixels. the specs can be found here