A phone case featuring a starry night sky with mountains sounds beautiful! Here's a design idea for you:
Imagine a glass phone case with a deep, midnight blue background transitioning into a gradient, showcasing a starry night sky. Bright stars and constellations are scattered across the sky, twinkling in different sizes. In the distance, dark silhouettes of mountain peaks create a serene, natural horizon. The glass would give it a sleek, polished finish, making the stars and mountains look almost three-dimensional.
Would you like me to help you visualize this design further or add any specific elements?