I think rich banners make the new theme work much better visually. Have a look at the following:
These seem to fit in much better with the new theme than our much-adored but now overstretched text-and-tape. In contrast, look at the following text-dominated beta sites - they look clinical and unappealing:
Even a fairly 'small' or plain graphical elements can help:
For EL&U, consider using a (faded? beige? sepia? wood-dominant?) picture of an old library.
Here's (a link to) a collection from shutterstock. The expansive panorama of the Rijksmuseum Library gives a flavour of what I'm talking about. (Please excuse the lack of pictures; I'm not familiar with shutterstock's policies regarding reproducing images on unrelated sites.)
Having an olde worlde picture as the banner would also lend a touch of class to the site, perhaps subtly encouraging questions and answers to live up to it.