When drag a nivo slider or any slider onto a page you have the option to stretch to fit you width but when i add pictures to it, it does not look right in the slider. is there a way to change the box that the picture gets copied to?

For instants my pic is 1334 x 264, i can stretch the slider to that size but if you double click to edit the pics you can see the picture is bigger than the box it goes into. How can i make the boxes that you drag and drop the pics into the same size as the pic so it looks right when viewing

Is there another alternative slider. I just have three pics that i want to automatically go to the next pic without any dots or numbers to change it your self. Is there a simple way just to somehow make three pics change with out a slider box?