i had the same problem... every time that i wanted to publish my css.. I had to make a search/replace.. and relative path wouldnt work either for me because the relative paths were different from dev to production.
Finally was tired of doing the search/replace and I created a dynamic css, (e.g. www.mysite.com/css.php) it's the same but now i could use my php constants in the css. somethig like
.icon{
background-image:url('<?php echo BASE_IMAGE;?>icon.png');
}
and it's not a bad idea to make it dynamic because now i could compress it using YUI compressor without loosing the original format on my dev server.
Good Luck!