iSticker bring up some very popular sticker packs such as memes, rage comic, flat icon, troll face,... and so on.
The best thing is iSticker can update new sticker packs automatically. You can access new sticker pack within the app. It is easy to use.
iSticker also manage all of your sticker packs, you can download more, remove the old one,... to keep update with new trends.
iSticker for iMessage