Rules first, design second:
• Business-standard file set-up is a 300 dpi, CMYK color profile
• The standard DVD insert size is 7 1/4'' x 10 3/4'' AFTER it's been cut out, so include a minimum background extension of 1/8'' to 1/4'' to guarantee that you won't make your design too small and have white edges when it's cut (this is known as including bleed).
• The above measurements are intended for designers working in a printer's spread format, meaning that the cover is on the right, the back the left, and a 1/2'' spine separates them at dead center.
• The DVD's spine text should be rotated to 270° (or -90°) so that if the case is placed face-up on a table the spine is readable.
Design:
I'd suggest using a solid color fill, a textured color fill, a gradient fill, or a high-resolution background image.
Your color scheme should reflect the school colors and whatever photos are included on the cover should be examples of the school's best attributes, whether that's the football team or the school band. A picture of the front of the school itself would easily be appropriate.
Avoid using overly-elaborate font styles or difficult to read colors (like red text on a black background). The size of the text should NOT drop below 6 pts. If there's too much text to fit in 9 pts or less... there's just TOO MUCH.
If it were me, I'd use a picture of a panther leaping towards the viewer from the cover of the DVD and either nothing but color fill and/ or text in the back, or the same panther, but with a 50% transparency.
Hope that's helpful!