geminiで下記のプロンプトとお気に入りの画像を使って例のような画像が生成できます。
生成した16パターンの画像をこのアプリに通すと、16個のスタンプに切り分けて、透過pngにします。

target_model: "Nano Banana Pro"
task: "Sticker Style Sheet Generation for Global Audience (Comment Edition)"
aspect_ratio: "1:1 Square"
style: "Kawaii chibi character digital illustration, clean vector lines, soft pastel colors, spring-themed. Each sticker has a thick white outline. Vibrant and expressive."
grid_structure:
layout: "4x4 grid (16 distinct stickers on a single sheet)"
background: "Clean, solid soft mint background"
stickers_content:
row_1:
- sticker_1: "Chibi character jumping with stars, Text: 'すごい！'"
- sticker_2: "Chibi character with cool sunglasses and a smirk, Text: 'かっこいい！'"
- sticker_3: "Chibi character leaning back confidently, blue sparkles, Text: 'クール！'"
- sticker_4: "Chibi character with sparkling eyes and rose petals, Text: 'ビューティフル！'"
row_2:
- sticker_5: "Chibi character bowing with a heart, Text: 'サンクス！'"
- sticker_6: "Chibi character giving a big thumbs up, Text: 'いいね！'"
- sticker_7: "Chibi character holding a trophy or medal, Text: '最高！'"
- sticker_8: "Chibi character applauding with a big smile, Text: '天才！'"
row_3:
- sticker_9: "Chibi character with wide eyes and open mouth, shocked by beauty, Text: '神！'"
- sticker_10: "Chibi character with heart-shaped eyes, Text: '大好き！'"
- sticker_11: "Chibi character blushing and hiding face, Text: '尊い...'"
- sticker_12: "Chibi character with a fist pump and fire background, Text: '激アツ！'"
row_4:
- sticker_13: "Chibi character crying happy tears, Text: '感動！'"
- sticker_14: "Chibi character winking and pointing at viewer, Text: 'センス◎'"
- sticker_15: "Chibi character looking through a magnifying glass, Text: '神作！'"
- sticker_16: "Chibi character throwing flower confetti, Text: 'おめでとう！'"
text_rendering:
font: "Playful, bold, hand-drawn Japanese bubble typography"
placement: "Text is clearly integrated within each cell, easy to read"
accuracy: "Render exact Japanese text with correct characters"
output_quality:
details: "Meticulous character expressions suited for reactions, professional sticker layout, high-end vector aesthetic"

1)chibi