GIPHY for iMessage - The easiest way to share all the GIFs in all your txts
Stickeroid - Rate Everything
Doll Up Stickers - Dress up your messages.
Sticker.Place API - Get stickers for your app
Bobble Stickers for iMessage - One selfie, Unlimited Stickers!
Sticker List - Discover the best stickers daily and publish your own.