1) We can not accept images that violate Apple or Google T&Cs, e.g. no objectionable content or copyrighted material. https://developer.apple.com/app-store/review/guidelines/
2) We really appreciate compressed images (max 400kb images)! You can use a tool like ImageOptim to compress yours: https://imageoptim.com/
3) We accept sticker packs with a minimum of 12 stickers included.
4) Please provide all required assets and stick to the following image guidelines:
The required assets are stickers, sticker market banner, thumbnail & metadata: https://prnt.sc/pu9hom
For the NON-ANIMATED STICKERS: PNG format. Each sticker should be 280 x 280 pixels in size. Transparent background.
For ANIMATED STICKERS: GIF format. Each sticker should be 280 x 280 pixels in size. Transparent background.
For the STICKER MARKET BANNER: JPG or PNG format. 1280 by 800 pixels in size. A good banner showcases your stickers, helping your pack to stand out.
For the THUMBNAIL: JPG or PNG format. 128 by 128 pixels in size. The thumbnail is used primarily to identify your pack in the menu once purchased. Should be readable even at smaller sizes.