Create a cinematic YouTube channel thumbnail (16:9 landscape) based on the uploaded image of an epic Ukrainian Cossack on horseback holding a large blue-and-gold flag with a golden trident (Tryzub), silhouetted against a dramatic sunset sky with dark storm clouds and a distant charging cavalry army. Extend the scene naturally to the sides to fill a wide 16:9 frame, keeping the Cossack and flag as the dominant hero element on the left third. Boost the epic cinematic mood: golden hour rim lighting, glowing sunset, dramatic dark clouds, atmospheric dust and mist, rich painterly detail, high contrast and vivid colors optimized for eye-catching YouTube thumbnails. Leave clean negative space in the upper-right / center area for a channel title or headline text overlay. Ultra-detailed, dramatic composition, high quality.
