Consider... Real flowers
If you're using real blooms to decorate your wedding cake, first of all, choose ones which are edible. You don't want to fall in love with your flower selection only to find out that the ones you have chosen are poisonous! Ones to avoid include hydrangeas, larkspur and lily of the valley. But don't worry, there are many flowers that are safe to put atop your cake such as carnations, dahlias, geraniums and, of course, roses.
A plain wedding cake is the perfect canvas for fresh blooms and for extra points, make sure the flowers on the cake complement your bouquet and tablecentres.