How do i add an image to the Twenty Eleven theme header?

I am trying to add an organization logo to the left of the Title and Tag line. I have tried editing the header.php and style sheet to no avail.

Is it possible to insert an additional picture into the Twenty Eleven header? (I do not want to replace the header image, I want to add another image, our logo, above the header image.

I have tried adding the image both directly as an image in the header.php, in which case it appears much larger than the actual image and does not respond to sizing.

<img id=IRPS-logo" src="/wp-content/uploads/2013/12/IRPS_Logo.png" alt="IRPS Logo" width="150" height="150">

I have also tried adding a <div> and specifying the background image, but the div does not seem to render.

header
<div id="IRPS-logo"></div>
css
#IRPS-logo {
margin: 20px;
width: 150px;
height: 150px;
float: left;
background: url('/wp-content/uploads/2013/12/IRPS_Logo.png') no-repeat left;
border: blue solid 3px;
position: absolte;
top: 20px;
left 25px;}

Any help is greatly appreciated.