If your image is still over 20 Kbs, then you need to resize the image. The first thing to remember is that if the photo takes up more than one screen on your web page, you've wasted your efforts. Besides, if the photo's larger than one screen, I can guarantee you it's far larger than 20 Kbs. The very largest images I use on our site are about 275 pixels on their longest side, and this size is often almost always less than 20 Kbs. A good way to put many images on your web page is to use thumbnails.
Thumbnails are little tiny images that are linked to the larger image.
In other words, when you click on the thumbnail, you go to another screen which shows you the full sized image. Thumbnails are great, but a lot of people do them incorrectly. In order for any image to come up as quickly as it can, you need to measure both the width and heighth of the image in your HTML code. It takes as long to load this incorrect thumbnail as it does to load the larger image. People will be groaning because your page will take so long to load.