I'm not a fan of banners at all, but if you are gonna have them, then they are fine.
Once the cover is in a box, the spine is seen as a separate entity, so where they end is personal choice.
The synopsis might look better slightly smaller, and curved on it's right side to match the curve of the blue "stars" panel.
The single pic on the back looks a little lost all on it's own there. Maybe two or three smaller ones blended together? And maybe framed in some way, rather than just dropped there. If that meant reducing the size of the special features box, that might be worth doing.
You got the makings of a cool cover there. (IMG:http://www.hirescovers.net/forum/style_emoticons/default/thumb.gif