Shortcode plugin [retour] for a unified link to top style.
Sure. Just replace the arrow.png file in the plugin's folder by your own arrow.png.
I suggest changing slightly the code of your header. After the
<body> tag, look for the following code:
<a href="<?php echo home_url(); ?>">, and change it for
<a href="<?php echo home_url(); ?>" name="top">.