Well I checked it out... just add the CSS below into your custom stylesheet.

It gets rid of the purdy wowhead borders, but you can add your own squared off border by changing the style of the border below (color in red). Change the URL to your background image in orange.

div.wowhead-tooltip {border: #ffcc00 1px solid;}
div.wowhead-tooltip table td, div.wowhead-tooltip table th {background: url(http://i259.photobucket.com/albums/hh311/hotwow/themes/styles/bkgd_stone1.jpg);}

If you want to keep the wowhead borders, use the CSS below. The onlydisadvantage is that there is still a blue transparent edge around yourbackground image.

div.wowhead-tooltip table {background: url(http://i259.photobucket.com/albums/hh311/hotwow/themes/styles/bkgd_stone1.jpg);}

I don't think you'd be able to make a different background image for each link, but you could make it look different on each tab of your site - just add the CSS above (wrapped with <style type="text/css"> and </style>) into any free form text/css box on that page.

Got a link to your site so I can look?

Ok, now that I've had a closer look (with actual images o.O LOL)

I see that the background image repeats with what I had above... that's also where the black line came from. So I messed around with it and figured out how to move the icon inside the window.



Just paste this code into your Custom StyleSheet or into a Free Form Text/HTML box on the page you have wowhead links.

div.wowhead-tooltip p { position:absolute; top:5px; left:85%; }
div.wowhead-tooltip { border: #ffcc00 1px solid; background: #000000 url(http://i297.photobucket.com/albums/mm228/jason3223/whitewings-1.gif) no-repeat; }
div.wowhead-tooltip table td, div.wowhead-tooltip table th { background:transparent; }