1. Go to Blogger Dashboard.
2. Click on your Blog Title.
3. Now jump to Template tab.
Note: Before editing your template, you may want to save a copy of it. Read How to Back Up Your Template.
4. Click on Edit HTML button.
5. Now find <data:post.backlinksLabel/> data layout tag in your template and just replace it with the text or an image you are about to.
Note: If you prefer image there, just specify image tag as <img src="[URL of Your Image]" alt=""/> by replacing data layout tag.
6. Now Save template and you can see your text on post pages just above backlinks.