It really depends on the size of the pic. If it is a large image you have no choice but to either shrink it or loose quality. If you save a pic as a .jpeg and use a quality of 9-10 then you will shrink the file KB size about as much as possible without loosing too much quality (only a few artifacts should be able to be seen). Also I am not sure why but sometimes in small images (such as an avatar) I get smaller results from a .png (crazy I know) so my suggestion is save the same file under different formats and see if that helps. That is about all you can do
