Log in to your dashboard--> layout- -> Edit HTML, scroll to where you see this:-
<b:if cond='data:top.showAuthor'>
<data:top.authorLabel/> <data:post.author/>
</b:if>
Replace
<data:post.author/>
in the code with :
<a href='URL OF YOUR PROFILE'><img src='URL OF YOUR IMAGE' style='border:0'/></a>
Remember replace "URL OF YOUR PROFILE" and "URL OF YOUR IMAGE" with your details.
This gives you a signature at the bottom of your post and links it to your Blogger profile.
File Under : change template, image, post