Sometimes a cake design one hundred percent revolves around what the guest of honor wants for their birthday or event. This means letting go of perfection or creating a cake that might not be shown in your portfolio.
For example, an icing covered snow scene cake for a 10th birthday should have all the design elements the child wants and the layout he requests. The bottom line for any cake is it should delight and fulfill the people it has been made for rather than your ambitions or vision. You can advise but not decide on the look of the cake unless you have permission.