To set transparent background color for the Carousel set the background option to transparent. You must also set the wmode parameter of the embedding code in the html page to transparent. [ xml]

Tip: if you don't mean to put a border around the carousel (like I did in the above example using CSS styles of a container div) I suggest you to set the bottom margin so that the reflections do not get outside the Carousel area. [ xml]

Enjoy my Carousel, Saverio.