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/AVvXsEgQkjn4cKWGxBcPSqN0CMnEhLjDYTJDb8x09DTYXVXUieXnex2KqerqKrin674m-aYNJkCqnrqFLUHyNcC6Dcs4CgdSS8oegdqLuBdIsRScqjL8I6xNu39feEMmTD550Cx48ia0mG5_qOI/s1600/Slide9.JPG');
background-position: center; 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>