So you put a background image to the Header section and define a height with CSS. Negatives (which you're using) has a #header defined, and I know Transmogrified does, so simple trick of aligning it into the right bit.

This should work:

#header {
background-position: center bottom;
background-repeat: no-repeat;
background-image: url(http://taktix.org/images/header-tlrt.jpg);
min-height:100px;
}

Replace your image with mine and change the height to suit, obviously.

No idea how to rotate it though, sorry.