As some of you might already know, it is impossible to add artwork to files of the 'Internet audio stream' variety using standard means available in iTunes. I have discovered (at discussions.apple.com) a way of tricking iTunes to make this possible.
I have several Internet radio streams and none of them have artwork. I thought that a nice picture would look better in Cover Flow, instead of the default gray square with a note on it.
How to do this: add matching album and artist tags to some random track in the library and also to the stream. Then add an image (the one to be used for the stream) to both files while 'editing info for multiple files.' The image is then added to both files.
Then return the random track to its old tags. The stream's artwork will disappear. Do one last step -- rename the stream to its original name, deleting its artist and album tags (since it is a radio station stream, these tags were empty initially). The artwork should reappear, in List, Grid, and Cover Flow views.
[crarko adds: I haven't tested this one.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100624124620212