Resizing elements backgrounds with jQuery is simple!

resize.js

function resizeBackground(elementsOrSelector, sizeMultiplier) {
	$(elementsOrSelector).each(function(){
		var el = $(this);
		if (el.css('background-image') != 'none') {
			resizeBackgroundProperty(el, 'background-size', sizeMultiplier);
			resizeBackgroundProperty(el, 'background-position', sizeMultiplier);
		}
	});
	
	function resizeBackgroundProperty(element, property, multiplier) {
		var bgSizes = element.css(property);
		bgSizes = bgSizes.split(/\s*px\s*/);
		bgSizes = bgSizes[0]*multiplier + 'px ' + bgSizes[1]*multiplier + 'px';
		element.css(property, bgSizes);
	}
}

Resizing elements backgrounds with jQuery

Why use plugin in a separate file for something that takes less than 20 lines of code?