If you're shooting for a true, classic craftsman trim style, keep it basic. Craftsman window trim was typically made from large, flat, straight boards, either sanded smooth or rough-hewn. Square-edged moldings are often featured around both windows and doors. For a more elaborate look, use multiple square boards to create a more layered, stacked look.
Although window trim in the craftsman-style home was often simple, craftsman homes often included small details carved or added into the woodwork to add beauty to the home. To keep with the elegance of the craftsman style, carvings should remain simple and have the "arts and crafts" feel, such as a basic flower design carved into the top corners of the window trim. For a more basic look, create curved, carved pieces to add to your window trim.
Whatever window trim style you decide on for your craftsman-style home, remember to keep it proportional. One of the key elements of craftsman design is keeping the sense of proportion and design. Heavy wood carvings, very elaborate trim or overpowering trim elements do not work with the craftsman style.