Copy this code and put it in an "HTML" gadget. If you need detailed instructions go HERE.
<style type="text/css">body
{background-image: url('https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWcTnffKMcXj3uotGHzf24gq_FRH8przF4IkYd6PRmSOp22Ris3xWShyphenhyphen0-I7gwXnttIMyyFq_0BPlwSjguIAwuzwtI7lmrvITfAyGzgoFIZLkLoWBaN1AOJ8t30sNFKpGfJ5Uzg7llMIQ/s1600/Slide8.JPG');
background-position: top; background-repeat: no-repeat; background-attachment: fixed; }
</style><div id="tag" style="position:absolute; top:30px; left:0px;
border:0px;">
<a href= "http://www.designsbyfarmgirl.blogspot.com" target="_blank"><img border="0" src="http://i1213.photobucket.com/albums/cc463/MNFarmGirl/backgrounds/DBFGLogo.gif" width="185"/></a></div>