To add a signature or image, first, you need to have image or signature and upload it somewhere like Flicker, photobucket or in your FTP. Then follow the below steps..
1. Go to your blog inside the Blogger Dashboard and click on design.
2. Then click the Edit HTML button.
3. Check the Expand Widget Template box.
4. Find by Click CTRL-F and copy and paste the line below in the search box to search for it in your code.
post-footer-line post-footer-line-1
<div class="post-footer-line post-footer-line-1"></div>
<img alt='flower' src='http://www.imagesource.com/flower.jpg' style='border: 0;'/>
<a href=’http://www.xyz.com/flowers’><img alt=’flower’ src=’http://www.imagesource.com/flower.jpg’ style=’border: 0;’/></a>
You are done!
Source:sociablweb