Classic Shell runs on Windows 7 also which is why you might have thought it gives you back the 3D retro look.
You will need to install a freeware first like UXStyle (
http://uxstyle.com/) which lets you use custom unsigned themes and then install/apply one of the themes Jcee mentioned above. There are many themes at Deviantart.com but note that any theme only works with a specific OS, so a theme made for Windows 8 will not work with 8.1. A theme made for Windows 7 will have to be updated for Windows 8 too.
Disclaimer: Anything that happens to your PC from using third party software recommended in the Classic Shell forum is purely your responsibility.