Is there a site or program I can use to decorate my own wedding cake for free?

I am a very creative individual and I'd love to virtually decorate my own wedding cake. We don't have a date yet (other than being on the first day of fall) so I really didn't want to spend any money on a site, but if I have to, I will. Of course, I don't want to actually bake and decorate due to the millions of other things a bride has to do, but I have always had a knack for food art as I am a chef. Any ideas of a free site or free program I can use to virtually decorate my wedding cake? Or even just to decorate any cake for that matter?