Not true...it is possible to change the look of iTunes, however there isn't a real straight forward way to do it. The most popular is to download a modified .rsrc file and replace iTunes' existing one. This however requires that the user back up both the replacement and original files as with updates to itunes (and some UI theme changes) the .rsrc file will be overwritten.
@ bigrobb: Check these out ->
http://macthemes2.net/2008/04/21/plexis-shine-themes-hit-itunes/
I'm fairly certain the disclose instructions on updating your jukebox, but if not:
Before you do anything, if you have iTunes running...quit it.
1. Find your iTunes application, right click and "Show package contents"
2. Navigate Contents/Resources and backup "iTunes.rsrc"
3. Replace the old .rsrc file with the new one.
4. And your done! Restart iTunes to admire your handywork.
