Create a gritty, vintage-style t-shirt design featuring a hand-drawn sketch of a retro motorcycle with intricate details that highlight its classic character. The motorcycle should be the focal point of the design, showcasing its vintage essence.. Utilize muted shades of grey, maroon, and burnt orange to create an old-school, rugged look that resonates with motorcycle culture. The overall atmosphere should be gritty and vintage, appealing to motorcycle enthusiasts. Employ pencil sketch techniques with digital texturing to enhance the vintage feel, adding depth and character to the design. The background must remain transparent for easy application on various t-shirt colors, making it perfect for a casual, rugged look.