Abstract: A modular composite panel and system of panels provides an aesthetically pleasing wallboard, ceiling, or other covering for an interior surface of a building. The panels are made from a hardened gypsum based skin moulded with a lower density backing material. The panels have a three dimensional relief and can be abutted together to form a system of panels. An experienced installer can use a filler that has a vinyl or acrylic additive to fill the seams between the panels. The installer can then sand the seams and adjacently located regions, as necessary, to create a continuous, seamless three-dimensional surface. Each panel is capable of receiving paint or texture, or being cut, trimmed or machined.