I don't have stunning photos of Sestri Levante; every time I went there, it was cloudy and grey. However, this should not discourage you from visiting this picturesque ligurian town. Sestri Levante is actually quite big with close to 20,000 inhabitants but you should concentrate on the old part on the peninsula.
From the railway station head towards the sea. You will soon find yourself on Via XXV Aprile with cute little stores and seafood restaurants. This main street runs towards the end of the promontory and if you turn left or right, you will get to one of the famous bays of Sestri Levante: Baia del Silenzio (Bay of Silence) to the east, and Baia delle Favole (Bay of Fables) to the west. The Baia delle Favole was named in honour of the Danish writer Hans Christian Andersen who lived in Sestri for a while in 1833.
I've just read a list of the most beautiful beaches of Italy, chosen by Italians. Baia del Silenzio was on the list as the only beach from Liguria. I don't quite agree; in my opinion there are some more beautiful beaches in Liguria but this bay is surely one of the most famous ones among Italians. And yes, it is very pretty with the colourful houses and its sandy beach. It is also a favourite spot of local people. When the water is too cold for swimming, they are just having a picnic or playing ball games with the kids. Baia delle Favole is bigger, with a long sandy beach and a nice promenade.
If you enjoy hiking, don't miss the trail to Punta Manara. Look for the sign on the left side of Via XXV Aprile as you are walking towards the old town. It's a very nice hike, mainly up on the way there. From the viewpoints, you will enjoy the most magnificent view of the promontory and the Baia del Silenzio.