I did one for my band a while back..get the cover off of and existing CD, and measure the front, back, and spine. These are your parameters. Anything that fits in there (well, subjet to your artistic representations) should work. You'll need to be able to affix text vertically for the spine, but everything else should be on the horizontal. Getting fonts to look good at the 'fine print' level can be a pain, you usually have to do the smallest stuff in some sort of 'sans-serif' font, or you can't read it.
Make sure that your design catches the eye, something that draws your attention; since it has to compete with other CDs for someones' dollar (or sheckle, or whatever..;). Since it's only about 5.25" (if'n I remember correctly, it's been about 8 years) square, a lot of the details may not show up at such a small size. It's something to think about.
I suppose you can do an inside sleeve to put in most of the textual info, but again, it's your design. I know this doesn't sound like help, but charge enough to let them know you're serious (you may want to discount slightly for the first one, then up the price later when you're 'established), but not so much that you scare them away..hope this helps.

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)