Make sure that the source picture is no bigger than 120 pixels in any one direction. You will need a photo editor program to shrink your image to size. Crop off all extraneous image so that your subject does not dissapear into obscurity at this small size.

Notice that i have the bumpers touching the sides of the image to try to get the subjest as large as possible. The height wasnt a problem as the width is about twice as big, so a little background above & below doesn't matter.