<plugin name="bannerRotation">
        <!-- supported positions: left, top, right, bottom -->
        <position>top</position>
        <!-- for top and bottom positions width must be greater than height    -->
        <width>400</width>
        <height>64</height>
        <banners>
            <banner>
                <img>http://localhost/files/banner1.png</img>
                <link>http://www.google.com</link>
                <time>20</time> <!-- in seconds -->
            </banner>
            <banner>
                <img>http://localhost/files/banner2.png</img>
                <link>http://www.yahoo.com</link>
                <time>25</time> <!-- in seconds -->
            </banner>
        </banners>
    </plugin>

Plugin is designed to rotate pre-set list of banners therefore can't be used for running commercial adds, like AdSense.