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/AVvXsEi5JzuswaBeAIC2jOV3YYVqa5cFTuD2nG2NvMukiG5p6dEyeKxcEudnBYjE_64oCoOqW_zrAz-G8fY0FxbImW82J2PjLik6EbG21UEArbqvMNPYCSAT_mFw8aeOxf0k4c63iycDGl5aamA/s1600/Slide2.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>