Link to my original blog post:
http://www.systemsarchitech.com/article/33/create-your-own-custom-boot-image
This is a great idea for consultants who want their companys logo to be plastered during a scripted boot sequence. It takes a bit of work but I think its definitely worth it.
Follow these instructions for creating your custom CD. The location of the image file is in /isolinux, filename = splash.lss.