The following tutorial covers changing top image in Berry Responsive Theme on a Plone 4.2 website.
Berry theme includes an image that is used in the top area throughout the whole site. You can also set your own one for each site section separately.
To replace this image, add an image to the desirable location. Note, add an image to the site root with the image shortname/id topimage to set it as a top image globally; if added to a certain folder, image will be displayed in this folder only. Dimensions recommended for top image are 960рх*170px.
Make sure image shortname is correct, otherwise image will not be shown on the top area.