This is for anyone who uses the "Apple_Legacy_CD.iso". I made an icon for it.
It's a PNG, so you can just download it, open it in Preview (or similar app), select all, copy, and paste it into the info panel of the Apple_Legacy_CD.iso file.
To make it the icon of the CD when you insert the disk (must be done before burning the disk, mount the ISO to your desktop first (you may need to convert to a read/write disk first), then follow the steps above.
I have hundreds of custom icons for everything from System 7 CDs, through every version of OS X, to folder icons. Let me know if anyone's interested in me posting them. I was going to start a website, but haven't gotten around to it yet.