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/AVvXsEho8nBmCKVxHYbR8V2AkDKRAcElG6N3uvM36PGuGYP9GSWjbDu3eGAs5bszsj8h91o1kl2IVA8BI4mGTLAfM6KM1iOuFzeKzIcC9yTiazQGJWb811uuhEZqri7eqjjsnd0Du1zDD52sShA/s1600/Slide2.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>