Hi, if you open the cake in your profile that you want to change or delete there is a symbol a little square with a pencil which is on the right side of the name of the cake push on it and it will say edit. Underneath the photos of your cakes there will be a little rubbish bin push on that and it will delete that photo and then you can upload another one if you want. Hope this helps, not great on computer termanology. :-)
does this change any of the history of that cake ? (view/comments etc ?) I was wondering the same – wanted to change to watermarked pictures and not sure it if would affect things like the widgets etc.