After the music, the next biggest means of expression is the cover art. This used to be referred to as a sleeve, but as vinyl has diminished in popularity, it is more typically referred to as cover art. There are various approaches to creating memorable and eye-catching cover art. Some artists pick a theme and stick with it throughout their entire career. For example, each Iron Maiden album cover featured the same typeface and image. Other artists aim for a more abstract concept. Some use arty photos not directly related to the band, such as Roxy Music's cover for the album "Country Life." Others use the name of the band as the main inspiration of the art work, such as Daft Punk's album "Discovery." Pick something that is eye-catching and that communicates your aesthetic.
Use the inside of the booklet to give fans a chance to learn more about you. It's their reward for purchasing the CD. Since the size of the booklet affects the shipping costs of a CD, record labels have begun to limit the amount of pages their CD booklets have. However, you can use band pictures as background with information super-imposed on top, to save on pages.
It's traditional for a band to acknowledge those that helped them on their way. This is typically where each member thanks his parents, friends, spouse, teacher and even guitar repair man.
It's a matter of professional courtesy to acknowledge those that worked on your CD. This includes the producer, engineer, any session musicians and manager. If you list too many people, it can devalue the importance of being listed in the credits. Thank the kid who washes your car in the thank you list, and keep the credits for those involved professionally.
Some of your fans are musicians, too; this is why musical instrument manufacturers like to endorse high-profile musicians. Endorsement or not, it'll be interesting to people to know how you got that great guitar sound on track five, or why the drummer's cymbals sound so bright. Include a list of instruments, equipment and accessories.