Hi, I'm new-ish to 7, and I've just set up icons for all my Superbar buttons.
As I'm sure most users know, if you set your Superbar buttons settings to "Always combine, hide labels", then the different windows you've got open for any one application will appear in the little mouseover menu you get for that application's button.
Although I've set iTunes as a Superbar button, when it's open it doesn't acknowledge that iTunes is already "pinned" to the Superbar, and instead of running in my custom-icon button it opens in a second button with the original, boring iTunes logo (see attached screenshot)
I wouldn't really mind but I like having my Superbar icons match, without an odd-one-out.
Please note - Because I couldn't change the icons for the original "exe" files of each application, I just dragged shortcut files onto the Superbar (which you can change the icon for) that link to the original exe files. This doesn't affect any other program though - for example if I open a Word document the Word button on the Superbar highlights to show that I have it open, and new word documents open within the button's pop-up menu as they should.
Sorry for the length of all that - point is it's only iTunes that creates this problem and it'd be really good to hear people's suggestions =]