A letter S line logo design template would typically feature the letter S in a stylized, linear form. This could include elements such as clean lines, geometric shapes, and minimalistic design elements. The template could also include variations of the letter S in different font styles and colors to provide options for branding and marketing materials. Some examples of this type of logo design include logos for companies or products that have an "S" in the name, or logos that use the letter S to represent a specific concept or idea.