I used gel food color to paint on fondant for this cake.  One of my friends wanted a birthday cake with a picture of her bosses bird on it.  You can take clear vanilla extract and gel food color to paint on fondant like water colors.  The clear vanilla extract will dry in just a few minutes.  The flowers were also fondant made with a cookie cutter.   If you can’t draw very well you can always photocopy the image you want to put on your cake.  Cut the picture out and then lay it down on the fondant to get the basic shape.  If the picture is more complex then cut it in sections and lay those out as guides to outline where you want to paint.  This type of cake will be something that they will love and talk about for years to come.