Ah, I see.
iTunes doesn't pull down the artwork from a video podcast for display in coverflow. What you're actually seeing is a still frame from the (I think) first episode downloaded. It just happens that COW podcasts have the logo up on screen at the right frame that iTunes pulls the still.
At least this is my theory. None of the other video podcasts that I subscribe to (even Apple's own Tips video podcast) show album art.
Unless you have a special preference set. I could be wrong.
Jon
TreeLine Productions
Fort Collins, CO USA
Currently producing these popular podcasts:
"The Rest of Everest" Video Podcast *Voted as one of iTunes' "Best of 2006" podcasts
*Nominated for "Best Video Podcast" in the 2007 People's Choice Podcast Awards
http://www.therestofeverest.com
"Beyond the Movement: The Pilates Podcast"
http://www.thepilatespodcast.com