A lot of people find the new iTunes 10 icon unattractive and out of place. This hint goes well together with other hints about restoring what was preferred about iTunes 9.
This simple trick will restore your old iTunes icon (or you can replace it with another of your choice), and will work for any other app as well.
Right-click on iTunes.app and select 'Show Package Contents', browse to Contents/Resources and copy the file iTunes.icns to a safe location.
Now take the the old icon and overwrite the new icon with it. You will need to authenticate from an admin account to do this. The old icon can be obtained from an old version of iTunes, if you have access to a non-upgraded machine or a Time Machine backup.
You need to start and stop iTunes a few times before it picks up the new icon, and you might even need to reboot your computer.
A demonstration video can also be found on my blog.
[crarko adds: I haven't tested this one, but you can look at the video and see how it works. I'm one of the apparently few people who actually likes the new icon for iTunes 10.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100903020407255