Flexible, 4:3 container with images that fill. Images 'letter box' if not 4:3

slideshow.css

.slide-media {
  	background: #000;
	text-align: center;
	width: 100%;

	// Intrisic Ratios. Used here to produce a flexible 4:3 box
	// http://alistapart.com/article/creating-intrinsic-ratios-for-video
	height: 0;
	padding-bottom: 75%;
	position: relative;

	.slide-media-inner {
		height: 100%;
		left: 0;
		position: absolute;
		top: 0;
		width: 100%;
	}

	img {
		display: inline;
		max-height: 100%;
  		max-width: 100%;
	}
}