Possible mold for window box

Is this too box like? I know it's called a window box but Don Gerardo thinks it can be made a little more elegant by adding sloping sides etc. It will be made of concrete. Perhaps it is possible to add some kind of detail to the front within the wooden form.

It is going to be hung from our bedroom window at the front of the house. It was Carolina's idea. I think it will look nice once painted and full of flowers.