img{
transform: rotate(20deg);
-ms-transform: rotate(20deg);
-moz-transform: rotate(20deg);
-webkit-transform: rotate(20deg);
}
<img src="http://msweb.moo.jp/wordpress/wp-content/themes/d-siori/img/css_img02.jpg" alt="サンプル" width="300" height="200" />