To provide an image link you will first have to create a button image.
Go to any of these sites and create a button image.
Free Gif Button Generator
After creating the button upload it to a free host like Photobucket.com or Googlepages and copy down the link to the image.
Paste it in a Notepad file for inserting it into the code as shown below.
To link to this blog, copy and paste the code below into your site.
Replace the CAPS with the relevant data for your blog.
Get Full Script HERE
I recommend that you use the link above - it's easier to understand :)