Backside graphics

On the back of the dvd cover you would usually have some sort of graphic to go behind the screenshots and text. This is usually in relation to the theme of the content.
Since my game is a sci-fi game i will compare some existing game cover art

A similar game to the style of the game i've gone with is Supreme commander
With this cover you will see that they went with a mixture of metallic and holographic looking graphics. This makes it look clean and futuristic.
http://www.covergalaxy.com/forum/attachments/pc/8106d1269682957-supreme-commander-german-supreme-commander-cover.jpg

With this cover they went with a full metallic look, using a rusted/worn look. This makes you think of armour or machinery.
http://www.covergalaxy.com/forum/attachments/microsoft-xbox-360/9890d1294800765-supreme-commander-2-pal-cover-disc-scans-supreme-commander-2-front.jpg

I also looked around for other covers that use other styles to make a sci-fi look but i couldn't find any. It seems that holographic and metallic looks are common themes in sci-fi graphics so i will have to design some for my cover.