A whimsical and dreamy watercolor painting of a sister sitting on a cloud, surrounded by fluffy white sheep and a few wispy clouds, with a big "Happy Birthday" banner written in cursive script, and a tiny birthday cake with a single candle burning brightly in the distance.

A vibrant and playful digital art piece featuring a sister surrounded by a swarm of colorful butterflies, each one representing a happy memory or inside joke between the siblings, with a giant "Happy Birthday" banner floating above her head, and a few strategically placed birthday candles and balloons in the background.

A warm and cozy illustration of a big, bright balloon bouquet with a big "Happy Birthday" banner in bold, colorful letters, surrounded by confetti and a sprinkle of glitter, with a smiling sister blowing out the candles on her birthday cake, set against a soft, pastel-colored background.