Design a vintage illustrated travel poster celebrating the beauty of Sifnos, showcasing its sandy beaches, and picturesque Cycladic villages. The style should pay homage to the classic travel posters of the mid-20th century, drawing inspiration from artists like Roger Broders and Tom Purvis. The lighting should be warm and inviting, capturing the essence of a perfect summer day. Use a color palette that includes vivid blues, golden yellows, and bright whites, reflecting the natural beauty of the Cycladic landscape and architecture. The composition should be well-organized, with a clear focal point --ar 9:16