I have tried and tried to resize a pic to use. I get the thing as small as a dot and it still says 21 kb at 45x47 pic size. How do you have a 100x100 image and bring the kb down to 15?
1) Visit: http://www.shrinkpictures.com/
2) Browse for the image and set the Custom max size to 100 and click "resize"
3) Check the size.
If that doesn't work, change the compression / quality of the image as an option to "good" and resize it again. If that doesn't work, change from jpg to gif or the other way around.