Assigning textures and materials within 3D scenes is a tedious and labor-intensive task. In this paper, we present Magic Decorator , a system that automatically generates material suggestions for 3D indoor scenes. To achieve this goal, we introduce local material rules , which describe typical material patterns for a small group of objects or parts, and global aesthetic rules , which account for the harmony among the entire set of colors in a specific scene. Both rules are obtained from collections of indoor scene images. We cast the problem of material suggestion as a combinatorial optimization considering both local material and global aesthetic rules. We have tested our system on various complex indoor scenes. A user study indicates that our system can automatically and efficiently produce a series of visually plausible material suggestions which are comparable to those produced by artists.