Have you ever visited a web site, enjoyed the results of hours of careful thought and creativity that have gone in to the design of the site, the colours, the layout - only to be jerked from your revery by a served advert which clashed with many of these aspects?
Nearly all work in ad serving concentrates to some degree on the fit of the product or brand being advertised to the content of the page or the behaviour of the user. However, wouldn't it be more satisfying if ads were either configured on the fly, or selected based on aesthetic qualities in addition to content and informational qualities?
The argument against this direction, of course, is that it is exactly that clash which draws attention to the ad and, therefore, results in a higher click-through rate. The great thing about the web is: that can be tested. Perhaps there are studies out there already on the impact of aesthetics on click-through.