Image Raw URL
Design and Skin Customization
This is the error itunes reports
Podcast artwork must be between 1400 x 1400 and 3000 x 3000 pixels, JPG or PNG, in RGB color space, and hosted on a server that allows HTTP head requests.
I know the image size, format, and color space meet the requirements..and I've validated the http header requests were working from a different validation site