General:
* Slippery slope
* Silent scream
* Stunning spectacle
* Sharp shock
* Solemn silence
* Sweet success
* Soothing serenity
* Sparkling stars
* Serene summer
* Sizzling summer
Nature:
* Serene sky
* Salty sea
* Springy sprouts
* Slithering snake
* Shady spot
* Sunny skies
* Spreading sunshine
* Snowy slopes
Food:
* Spicy salsa
* Sweet strawberries
* Savory soup
* Succulent steak
* Silky smooth
* Spiced sugar
* Salty snacks
People:
* Smart student
* Smiling stranger
* Strong swimmer
* Stealthy spy
* Successful salesman
* Scrupulous scientist
More creative:
* Serene symphony
* Stealthy shadow
* Sombre song
* Sprawling skyscrapers
* Splendid spectacle
These are just a few examples. You can be creative and come up with your own alliterations using the letter S.