In product design, sketches and images are strong devices for stimulating creativity. This paper presents a novel visual evolutionary computing environment to provide support for creative design. The 2D sketches and 3D images can be generated by combination of evolutionary computing technology and visualization technology in this environment. A tree-based genetic algorithm is illustrated by a reading lamp design example, which uses genetic algorithm with binary mathematical expression tree to form 2D sketches and programming using Visual Ctt6.0 and ACIS to generate 3D images. It shows that the approach is able to generate some creative solutions and demonstrates the potential of computational approach in creative design.