Check this one out:
It's simple, which I really like, and there are graphics on the front, the spine, and the back. However, I think the back of this cover is underutilized. The back is a great opportunity for marketing. Generally speaking, people picking up a book in a bookstore first look at the front cover, and then they turn it over to look at the back before they open it up. If the back cover is gripping and intriguing, there's a better chance that they'll continue investigating it and possibly even BUY it.
Here's an intriguing back cover:
The text boxes mimic the shape of the honeycomb, and the cover designer has included a teaser and endorsements. Very well done.
Of course, if I'm feeling vain, I could try a back cover that looks something like this:
I wonder if I could pull off that scholarly profile pose. There's only one way to find out. ;)