The <itunes:image> tag points to the artwork for your podcast, via the URL specified in the <a href> attribute.
Cover art must be in the JPEG or PNG file formats and in the RGB color space with a minimum size of 1400 x 1400 pixels and a maximum size of 2048 x 2048 pixels. Note that these requirements are different from the standard RSS image tag specification.
In ATP 103 around the 1hr mark, Marco Arment talks about the problems this results in for Overcast. We're dealing with the same issues.
iTunes recommendations (which not everyone follows) about the
<itunes:image>tag in podcast files: http://www.apple.com/itunes/podcasts/specs.html#imageIn ATP 103 around the 1hr mark, Marco Arment talks about the problems this results in for Overcast. We're dealing with the same issues.