Independent images on Zen's Sub-theme

Hello everyone,

I need some support, I'm really lost.

Now, I'm in the follow situation:

I have a drupal instalation (6.17), with Zen 6.x-2.0. And here at my work we developed a zen's sub-themes for ours websites, and now I need to find a way to change some images for each site, without need to make a copy of sub-theme for all of them.

Looking around I saw someone with the same problem (if I can call this a problem):
http://drupal.org/node/289538

In the first comment someone said to change the "base theme", the only place I found anything related in the sub-themes archive was in the .info file. If I follow his tip and change the base theme from zen to whatever the name of my sub-theme the site don't load anymore, stay in a blank page.

What I really want is, a sub-theme directory in the "/sites/all/themes/" folder, and in "/sites/www.site1.com/themes/" just the changes from the basic sub-theme.
What I got until now:

I can override the images I want to change with a subsubtheme.css, but I still need the .php files (page.tpl.php, theme-settings.php, template.php) on the local themes folder (/sites/www.site1.com/themes/). But those files are exactly the same of the "/sites/all/themes/subtheme/". What can I do to load this .php files from the subtheme folder at /sites/all/themes/subtheme?

I already tried call them in the .info file as a stylesheets, but didn't work.

Someone could help me?

Regards.

PS.: Sorry for the bad english and if I didn't make myself clear enough.