A more sophisticated (though still rather simple) way of storing (sensitive) data in an image file would be to include the data on the lower bit planes of the image. This would make the text, image, or animation (in the case of a .gif or some such animation) completely invisible no matter how much you zoom or tweak the image, unless you knew to reduce the bit depth to say, 2 bits at which point the hidden data would show.

See steganography for more details.