For doing so follow the steps below,

  1. Go To Blogger > Layout > Edit HTML
  2. Check the Expand Widget Templates box at top-right-corner
  3. Search for this,
<data:newerPageTitle/>
And replace it with this code,

<img src="URL-OF-PREVIOUS-BUTTON"/>
Now search for this,

<data:olderPageTitle/>
And replace it with this,
<img src="URL-OF-NEXT-BUTTON"/>
Then search for this,
<data:homeMsg/>
The above code will appear twice and replace both appearances with this code,
<img src="URL-OF-HOME-BUTTON"/>
Make sure to replace the URLs with the Image Links of your uploaded Images.
 
4.     Finally save your template and enjoy the new look!