PhotoStapler

PhotoStapler is a simple app that lets you select an album from Photos and turn its contents into a sticker pack for Messages. After you have selected an album to use as a sticker pack, any image you add to that album will become available automatically in PhotoStapler on iMessage, so that you can quickly drag and drop it into a conversation or just send it as a sticker.
PhotoStapler also comes with a built-in background removal tool: select any image in your album to use the tool powered by machine learning that automatically removes the background in the image, so that you can have nice transparent stickers to use on your messages.