I have noticed a few requests for Admin themes and I want to share a couple I made for my company's site. I would appreciate some feedback on any bugs or quirks with these before I commit them to the theme repository. The zip archive has two themes, Blue Glassy and Red Glassy. There are three core files that you'll need to replace. One is "modules\ThemeManager\action.defaultadmin.php". This file has a closing div tag added to the end of the file which fixes the missing tag when in the Themes module. Two additional files, "admin/editcontent and admin/addcontent", have a CSS classname added to the form tag. The edit/add content form tag in not embedded within the #page_content ID as it is in all the other form templates. The allows the bgcolor of the form and #page_content elements to toggle when the page edit/add mode. This basically keep the UI consistent. These changes do not affect the default theme. Back up these files first and upload the contents of the cmssimple_admin_theme to your root install dir.
I tested this on ver 1.14 and 1.2 using IE6+, FF2, NS7, Opera 8.5+ and Safari 3
http://trilogyaudiometrics.com/uploads/images/misc/cmssimple_admin_theme.zip