Since you have no background image on your body, it's easy to place one
in the top left corner.
This bit highlighted in red sets your background color as #fff, loads a background image, tells it not to repeat, position:fixed, left:0px top:100px;
background: #fff url(http://nopeople.com/files/canon-eos-496BG.gif) no-repeat fixed 0px 100px;
font:x-small Georgia Serif;
I'm sure you'll want to use a better image but you'll get the idea this way.
If you don't want this to be a background image of your body, you can present an image from your html and style that with position:fixed; and get the same effect.