If you have a photo with a non-square aspect ratio, and try to turn it into a sticker with the in-game UI, the cropping UI does not allow you to "zoom out" to allow the bounds of the sticker to extend beyond the smaller dimension of the image, and therefore forces part of the image to be cut off. Instead, it should allow the image to be shrunk to fit inside the sticker's 1:1 aspect ratio (or, unrestrict sticker aspect ratios).