Design a captivating coloring book cover for adults featuring a mosaic-style collage of intricate illustrations. Use a harmonious color palette with calming tones. Showcase elements like elegant animals, serene landscapes, beach scenes, cozy houses, graceful birds, vibrant flowers, and more. Arrange these designs in a balanced and visually pleasing composition. Apply subtle textures for depth, and incorporate a title in an artistic font that complements the overall aesthetic. Consider a size of around 2000x3000 pixels for a high-quality and detailed cover image.