Now that you have a functioning "style.css", "template.html" and "theme.php" you should verify that it is generating valid output.
Each of the following pages needs to be validated as an anonymous user, registered user, and in admin mode:
The following toolbars can assist you in validating the resulting output of your theme:
Internet Explorer:
Mozilla Firefox:
Your theme should now be ready to use with Coppermine 1.4.x