Just as a helpful note…you can put background images into the color boxes in the settings page. They work perfectly…just like a line of css. For instance I put in:
url(https://www.mysite.com/myfolder/images/tabhover.png) repeat scroll 0 0 transparent
Do NOT include the ending ; since the plugin adds this.
And I got some beautiful tabs with this method.
(I also tinkered with style.php in the plugin folder to increase some margins, add background color to the content div and put a line around it.)