You can't see this unless you're set to United States in your preferences, but it does look extremely like old Google, which is no bad thing.
If you click on the bing icon, though, you also go back to the landing page.
So this little bit of refinement seems to highlight the ever-changing-landing-image as a part of the bing experience.
Then Google copied the background image idea.
Now Bing has gone minimal, but there's obviously still some residual pull/desire around using imagery.
That little strip is a remnant. Like a human appendix it's a residual organ that wasn't completely eradicated as it evolved into the current design.
http://techcrunch.com/2010/06/09/google-adds-a-background-im...