Graphic Slider Size: How to change

Hi, Is there a way to change the size of graphic-sliders and their corresponding pictures? For example, the Ten Gauge is a 130 x 130 picture. I want to increase it to 260 x 260 and increase the size of the slider accordingly? Ultimately I want to replace the picture (which I know how to do in css) but I need to increase the size of the original picture to fit a larger one when replacing. Best, Rah