Bargello? The fabrics would look beautiful for one and if you just made you strip sets and started cutting random widths it would not be too "patterned".
Or if you want to get really crazy ( and maybe a bit smarty pants) you could take that darkest brown and make a big square in the center. Applique or embroider the word BOX on it. Then take the other colors and create blocks that depict things he likes to do and piece them all around the box.