Don't get me wrong, I love images. But I think there are limits. It has no compression. What is transferred is what is displayed. Thus it is good for pictures with great detail or lines.
Faces show up best with gif.
Gifs can also be saved at 256, all the way down to 2 colors and still look crisp. JPEG JPEG is a compressed format. That means it is sort of squashed together when it's put away. JPEG is best for pictures with bold colors and not much detail. JPEG is also good when you do offer large images.