Geekspiff has popped out a quickie bugfix version of ThemePark,
ThemePark 3.0.1.
The biggest thing this release does is restore a few window background elements that were missing from the 3.0 release when I consolidated all of the backgrounds together. The missing elements meant that themes exported from ThemePark 3.0 would not properly theme the area around controls in Carbon applications' drop down sheets. It also made the background area behind vertical tabs screwy.
To resolve these issues, just open your tpark file using ThemePark 3.0.1 and re-export your guiKit. No other action is necessary.