Create a captivating and serene desktop wallpaper that embodies the concept of a dark, cosmic expanse. The background should feature deep, rich shades of space that convey the vastness and mystery of the universe. Integrate subtle yet vibrant hints of rainbow colors, seamlessly blending them together to create a fluid and harmonious transition. These gentle hues should appear as if they are softly dancing across the cosmic canvas, enhancing the sense of tranquility. Introduce dynamic streams of energy and waves of light that flow gracefully through the scene, embodying a soothing and meditative ambiance. The composition should evoke a sense of healing energy, offering a visual respite and a calming influence to whoever gazes upon it. Ensure the overall design remains free of clutter and distractions, maintaining a focus on the ethereal beauty and peacefulness that a cosmic scene can convey.